Biometric image sensing

ABSTRACT

An novel sensor is provided having a plurality of substantially parallel drive lines configured to transmit a signal into a surface of a proximally located object, and also a plurality of substantially parallel pickup lines oriented proximate the drive lines and electrically separated from the pickup lines to form intrinsic electrode pairs that are impedance sensitive at each of the drive and pickup proximal locations.

RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. application Ser. No.12/820,100, filed Jun. 21, 2010, which is a Continuation-in-Part of U.S.application Ser. No. 12/688,790, filed Jan. 15, 2010.

BACKGROUND

The embodiment is generally related to electronic sensing devices, and,more particularly, to sensors for sensing objects located near or aboutthe sensor.

In the electronic sensing market, there are a wide variety of sensorsfor sensing objects at a given location. Such sensors are configured tosense electronic characteristics of an object in order to sense presenceof an object near or about the sensor, physical characteristics of theobject, shapes, textures on surfaces of an object, material composition,biological information, and other features and characteristics of anobject being sensed.

Sensors may be configured to passively detect characteristics of anobject, by measuring such as temperature, weight, or various emissionssuch as photonic, magnetic or atomic, of an object in close proximity orcontact with the sensor, or other characteristic. An example of this isa non-contact infrared thermometer that detects the black body radiationspectra emitted from an object, from which its temperature can becomputed.

Other sensors work by directly exciting an object with a stimulus suchas voltage or current, then using the resultant signal to determine thephysical or electrical characteristics of an object. An example of thisis a fluid detector consisting of two terminals, one that excites themedium with a voltage source, while the second measures the current flowto determine the presence of a conductive fluid such as water.

Since a single point measurement of an object often does not provideenough information about an object, it is often advantageous to collecta two-dimensional array of measurements. A two dimensional array ofimpedance may be created by moving a line sensing array over the surfaceof an object and then doing a line by line reconstruction of a twodimensional image like a fax machine does. An example of this is aswiped capacitive fingerprint sensor that measures differences incapacitance between fingerprint ridges and valleys as a finger isdragged across it. Such sensors reconstruct a two dimensionalfingerprint image after the fact using individual line information.

A simpler way to obtain a two dimensional image is to create a twodimensional sensing array. Such sensors however can be prohibitive incost due to the large number of sensing points needed in the array. Anexample of this is a two dimensional capacitive fingerprint sensor. Anumber of these are currently manufactured but use 150 mm² or more ofsilicon area and are therefore cost prohibitive for many applications.

These different types of electronic sensors have been used in variousapplications, such as biometric sensors for measuring biologicalfeatures and characteristics of people such as fingerprints, medicalapplications such as medical monitoring devices, fluid measuringmonitors, and many other sensor applications. Typically, the sensingelements of the various devices are connected to a processor configuredto process object information and to enable interpretations for objectfeatures and characteristics.

There are many applications for two dimensional image sensors as aparticular example, and innovators have struggled with state of the arttechnology that has come short of desired features and functions.Fingerprint sensors, for example, have been in existence for many yearsand used in many environments to verify identification, to provideaccess to restricted areas and information, and many other uses. In thispatent application, different types of fingerprint sensors will behighlighted as examples of sensor applications where the embodiment isapplicable for simplicity of explanations, but other types ofapplications are also relevant to this background discussion and willalso be addressed by the detailed description of the embodiment. Theseplacement sensors may be configured to sense objects placed near orabout the sensor, such as a fingerprint placement sensor that isconfigured to capture a full image of a fingerprint from a user's fingerand compare the captured image with a stored image for authentication.Alternatively, sensors may be configured to sense the dynamic movementof an object about the sensor, such as a fingerprint swipe sensor thatcaptures partial images of a fingerprint, reconstructs the fingerprintimage, and compares the captured image to a stored image forauthentication.

In such applications, cost, though always a factor in commercialproducts, has not been so critical—accuracy and reliability have beenand still remain paramount factors. Typically, the placement sensor, atwo-dimensional grid of sensors that senses a fingerprint image from auser's fingerprint surface all at once, was the obvious choice, and itsmany designs have become standard in most applications. Once thefingerprint image is sensed and reproduced in a digital form in adevice, it is compared against a prerecorded and stored image, andauthentication is complete when there is a match between the capturedfingerprint image and the stored image. In recent years, fingerprintsensors have been finding their way into portable devices such as laptopcomputers, hand held devices, cellular telephones, and other devices.Though accuracy and reliability are still important, cost of the systemcomponents is very important. The conventional placement sensors wereand still are very expensive for one primary reason: they all usedsilicon sensor surfaces. These surfaces are very expensive, as thesilicon material is as expensive as the material to make a computerchip. Computer chips, of course, have become smaller over the years toreduce their cost and improve their performance. The reason thefingerprint silicon could not be made smaller: they need to remain thesize of the average fingerprint, and the requirement for full scanningof the users' fingerprints simply cannot be compromised. The full printis required for adequate security in authentication.

Enter the fingerprint swipe sensor into the market. Swipe sensors arefundamentally designed with a line sensor configured to sensefingerprint features as a user swipes their finger in a perpendiculardirection with respect to the sensor line. The cost saver: swipe sensorsneed much less silicon, only enough to configure a line sensor with anarray of pixel sensors. The width is still fixed based on the averagefingerprint width, but the depth is substantially smaller compared tothe placement sensor. Some swipe sensors are capacitive sensors, wherecapacitance of the fingerprint surface is measured and recorded line byline. Others send a small signal pulse burst into the surface of thefingerprint surface and measure response in a pickup line, againrecording fingerprint features line by line. In either case, unlike theplacement sensors, the full fingerprint image needs to be reconstructedafter the user completes the swipe, and the individual lines arereassembled and rendered to produce a full fingerprint image. This imageis compared with a fingerprint image stored in the laptop or otherdevice, and a user will then be authenticated if there is an adequatematch.

For the capacitive swipe sensors, the first generation sensors wereconstructed with direct current (DC) switched capacitor technology (forexample U.S. Pat. No. 6,011,859). This approach required using twoplates per pixel forming a capacitor between them, allowing the localpresence of a finger ridge to change the value of that capacitorrelative to air. These DC capacitive configurations took images from thefingerprint surface, and did not penetrate below the finger surface.Thus, they were easy to spoof, or fake a fingerprint with differentdeceptive techniques, and they also had poor performance when a user haddry fingers. RF (Radio Frequency) sensors were later introduced, becausesome were able to read past the surface and into inner layers of auser's finger to sense a fingerprint. Different radio frequencies havebeen utilized by various devices along with different forms of detectionincluding amplitude modulation (AM) and, phase modulation (PM). Thereare also differing configurations of transmitters and receivers, onetype (for example U.S. Pat. No. 5,963,679) uses a single transmitterring and an array of multiple low quality receivers that are optimizedfor on chip sensing. In contrast another type (for example U.S. Pat. No.7,099,496) uses a large array of RF transmitters with only one very highquality receiver in a comb like plate structure optimized for off chipsensing.

One key impediment to the development of low cost placement sensors hasbeen the issue of pixel density, and the resultant requirement for alarge number of interconnections between layers of the sensor device. Atypical sensor for a fingerprint application will be on the order of 10mm×10 mm, with a resolution of 500 dpi. Such a sensor array would beapproximately 200 rows by 200 columns, meaning there would need to be200 via connections between layers in the device. While semiconductorvias can be quite small, the cost for implementing a sensor in siliconhas proven to be prohibitive, as mentioned above.

In order to produce a placement sensor at a low enough cost for massmarket adoption, lower cost processes such as circuit board etching mustbe employed. The current state of the art in circuit board via pitch ison the order of 200 um, vs. the 50 um pitch of the sensor array itself.Additionally, the added process steps required to form vias betweenlayers of a circuit board significantly increase the tolerances for theminimum pitch of traces on each of the layers. Single-sided circuits maybe readily fabricated with high yield with line pitch as low as 35 um,whereas double sided circuits require a minimum line pitch on the orderof 60 um or more, which is too coarse to implement a full 500 dpi sensorarray. One further consideration is that at similar line densities,double-sided circuits with vias are several times more expensive perunit area than single sided, making high-density double sided circuitstoo expensive for low cost sensor applications.

For laptop devices, adoption of the swipe sensor was driven by cost. Theswipe sensor was substantially less expensive compared to the placementsensors, and most manufacturers of laptops adopted them based solely onprice. The cost savings is a result of using less silicon area. Morerecently a substitute for the silicon sensor arose, using plasticKapton™ tape with etched sensing plates on it, connected to a separateprocessor chip (for example U.S. Pat. No. 7,099,496). This allowed thesilicon portion of the sensor to be separated from the sensing elementsand the silicon to follow Moore's law, shrinking to an optimal size, inlength, width and depth in proportion to advances in process technology.Although this advance in the art enabled cheap durable Swipe Sensors, itdid not overcome the basic image reconstruction and ergonomics issuesresulting from changing from a simple two dimensional placement format.In addition to Swipe Sensors being cheaper, they take up less realestate in a host device, whether it is a laptop or a smaller device,such as a cellular phone or personal data device.

In most swipe class sensors, the fingerprint reconstruction processturned out to be a greater ergonomic challenge to users and more of aburden to quality control engineers than initially expected. Usersneeded to be trained to swipe their finger in a substantially straightand linear direction perpendicular to the sensor line as well ascontrolling contact pressure. Software training programs were written tohelp the user become more proficient, but different environmentalfactors and the inability of some to repeat the motion reliably gaveSwipe Sensors a reputation for being difficult to use. Initial data fromthe field indicated that a large number of people were not regularlyusing the Swipe Sensors in the devices that they had purchased and optedback to using passwords. Quality control engineers who tried to achievethe optimum accuracy and performance in the matching process between thecaptured and reconstructed image found that the number of False Rejects(FRR), and False Acceptances (FAR), were much higher in Swipe Sensorsthan in placement sensors. Attempts to improve these reconstructionalgorithms failed to produce equivalent statistical performance toplacement sensors.

Other claims of the Swipe Sensor such as the use of less host realestate did not pan out. Various ramps, wells and finger guides had to beincorporated into the surfaces of the host devices to assist the userwith finger placement and swiping. These structures ended up consumingsignificant space in addition to the actual sensor area. In the end,swipe sensors ended up taking up almost as much space as the placementsensors. This was not a big problem for full size laptops, but iscurrently a substantial problem for smaller laptops and netbooks, mobilephones, PDAs, and other small devices like key fobs.

Real estate issues have become even more of an issue with mobile devicemanufacturers who now require that the fingerprint sensor act also as anavigation device, like a mouse or touch-pad does in a laptop. The swipesensor has proved to be a poor substitute for a mouse or touch pad dueto the fact that they are constructed with an asymmetric array ofpixels. Swipe sensors do a good job of detecting motion in the normalaxis of the finger swipe but have difficulty accurately trackingsideways motion. Off axis angular movements are even more difficult tosense, and require significant processor resources to interpolate thatmovement with respect to the sensor line, and often have troubleresolving large angles. The byproduct of all this is a motion that isnot fluid and difficult to use.

It is clear that low cost two dimensional fingerprint sensor arrayswould serve a market need, but present art has not been able to fillthat need. Conventional capacitive fingerprint sensors typically usedistinct electrode structures to form the sensing pixels array. Theseelectrode structures are typically square or circular and can beconfigured in a parallel plate configuration (for example U.S. Pat. Nos.5,325,442 and 5,963,679) or a coplanar configuration (for example U.S.Pat. Nos. 6,011,859 and 7,099,496).

These prior art approaches cannot be configured into a low cost twodimensional array of sensing elements. Many capacitive fingerprintsensors (for example U.S. Pat. Nos. 5,963,679 and 6,011,859) have platestructures that must be connected to the drive and sense electronicswith an interconnect density that is not practical for implementationother than using the fine line multilayer routing capabilities ofsilicon chips and therefore require lots of expensive silicon die are asstated before. Other sensors (for example U.S. Pat. No. 7,099,496) useoff chip sensing elements on a cheap polymer film, but the sensor cellarchitecture is inherently one dimensional and cannot be expanded into atwo dimensional matrix.

Another application for capacitive sensing arrays has been in the areaof touch pads and touch screens. Because touchpad and touch screendevices consist of arrays of drive and sense traces and distinct senseelectrodes, they are incapable of resolutions below a few hundredmicrons, making this technology unsuitable for detailed imagingapplications. These devices are capable of detecting finger contact orproximity, but they provide neither the spatial resolution nor thegray-scale resolution within the body of the object being sensednecessary to detect fine features such as ridges or valleys.

Conventional art in the touchpad field utilizes a series of electrodes,either conductively (for example U.S. Pat. No. 5,495,077) orcapacitively (for example US publication 2006/0097991). This series ofelectrodes are typically coupled to the drive and sense traces. Inoperation these devices produce a pixel that is significantly larger inscale than the interconnect traces themselves. The purpose is togenerally sense presence and motion of an object to enable a user tonavigate a cursor, to select an object on a screen, or to move a pageillustrated on a screen. Thus, these devices operate at a low resolutionwhen sensing adjacent objects.

Thus, there exists a need in the art for improved devices that canprovide high quality and accurate placement sensors for use in differentapplications, such as fingerprint sensing and authentication forexample, and that may also operate as a navigation device such as amouse or touch pad in various applications. As will be seen, theembodiment provides such a device that addresses these and other needsin an elegant manner.

Given the small size and functional demands of mobile devices, spacesavings are important. Thus, it would also be useful to be able tocombine the functions of a sensor with that of other components, such aspower switches, selector switches, and other components, so thatmultiple functions are available to a user without the need for morecomponents that take up space.

Still further, it would be also useful for different embodiments of atouch sensor to provide various alternatives for providing biometricsensors that are easy to use and feasible in different applications.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a diagrammatic view of one embodiment showing the drive andpickup plate structures with an insulating dielectric layer separatingthe drive and pickup lines.

FIG. 2 shows a basic diagrammatic view of one embodiment showing thebasic electrical field operation without an object in close proximity tothe drive and pickup plate structures with one drive plate excited by avoltage source.

FIG. 3 shows a basic diagrammatic view of one embodiment showing thebasic electrical field operation with an object in close proximity tothe drive and pickup plate structures with one drive plate excited by avoltage source.

FIG. 4 shows a basic diagrammatic view of one embodiment of the sensorshowing the differences in field intensity with and without an object inclose proximity to the drive and pickup plate structures with one driveplate excited by a voltage source.

FIG. 5 shows a basic diagrammatic view of one embodiment showing thebasic electrical field operation with an object in close proximity ofthe drive and pickup plate structures with the selected pickup plateamplified and all inactive drive and pickup plates grounded.

FIG. 6 a shows a basic diagrammatic view of one embodiment showing thebasic electrical field operation with a finger or object containing aridge surface feature in close proximity to the active electrode pair.

FIG. 6 b shows a basic diagrammatic view of one embodiment showing thebasic electrical field operation with a finger or object containing avalley surface feature in close proximity to the active electrode pair.

FIG. 7 shows a diagrammatic view of an x-y grid of plate rows andcolumns depicted by lumped circuit components that represent theelectric field couplings of the sensor at each drive/pickup crossover.

FIG. 8 shows an example of an embodiment of the placement embodimentusing a differential amplifier to take the signal from the selectedpickup plate and subtract it from a reference signal plate for noisereduction purposes.

FIG. 9 a shows the drive and sense multiplexing circuitry of anembodiment that incorporates a tank circuit to compensate for inputloading effects.

FIG. 9 b shows the drive and sense multiplexing circuitry of anembodiment that incorporates cascaded buffers to minimize input loadingeffects.

FIG. 9 c shows the drive and sense multiplexing circuitry of anembodiment that incorporates dedicated buffers for each sense tominimize loading effects.

FIG. 10 shows an embodiment that incorporates an analog receiver toprocess the sensed signal, and processing circuitry to perform the driveand sense line scanning function.

FIG. 11 shows an embodiment that incorporates a direct digitalconversion receiver to process the sensed signal, and processingcircuitry to perform the drive and sense line scanning function.

FIG. 12A shows one example of a layout of the drive and sense traces foran embodiment that incorporates the folded aspect of the embodiment laidout flat prior to folding.

FIG. 12B shows one example of a layout of the drive and sense traces foran embodiment that incorporates the folded aspect of the embodiment laidout flat prior to folding.

FIG. 13 a shows the layer stack-up of an embodiment that incorporatesthe folding aspect subsequent to folding.

FIG. 13 b shows an embodiment that incorporates the folding aspectsubsequent to folding and assembly into a rigid module.

FIG. 14 shows a sensor system configured according to the embodiment forthe purpose of sensing features of an object.

FIG. 15 shows an example of the sensing of a fingerprint features.

FIG. 16 shows the process flow steps required to collect a 2-dimensionalimage with a sensor system configured according to one embodiment.

FIG. 17 a shows the process flow steps required to authenticate a userwith a fingerprint sensor system configured according one embodiment.

FIG. 17 b shows the process of template extraction from a fingerprintimage typically utilized in user authentication applications.

FIGS. 18A-18D show an example of a fingerprint sensor system having anintegrated switch to allow a user to contact a fingerprint sensor and toactuate a switch simultaneously.

FIGS. 19A-J show another example of a fingerprint sensor system havingan integrated switch, a dome switch in this example, to allow a user tocontact a fingerprint sensor and to actuate a switch simultaneously.

FIG. 20 shows a top view of an embodiment of a switch formed on the samesubstrate as the fingerprint sensor.

FIGS. 21A and B are detailed views which show the operation of theembedded switch depicted in FIG. 20.

FIGS. 22-26 illustrate other embodiments of the invention.

DETAILED DESCRIPTION

As discussed in the background, there are many applications for a twodimensional impedance sensor, and the embodiment provides a broadsolution to shortcomings in the prior art for many applications.Generally, one embodiment is directed to a two-dimensional sensor, andmay also be referred to as a placement sensor, area sensor, 2D sensor.The sensor may have sensor lines located on one or more substrates, suchas for example a flexible substrate that can be folded over on itself toform a grid array with separate sensor lines orthogonal to each other.The sensor lines may alternatively be formed on separate substrates. Ineither or any configuration, the crossover locations of different sensorlines create sensing locations for gathering information of the featuresand/or characteristics of an object, such as a fingerprint for example.

In one embodiment, the drive lines and pickup lines are not electricallyintersecting or connected in a manner in which they would conduct witheach other, they form an impedance sensing electrode pair with aseparation that allows the drive lines to project an electrical fieldand the pickup lines to receive an electrical field, eliminating theneed for distinct electrode structures. The two lines crossing withinterspersed dielectric intrinsically creates an impedance sensingelectrode pair. Thus, the sensor is configured to activate twoone-dimensional sensor lines to obtain one pixel of information thatindentifies features and/or characteristics of an object. Unlikeconventional sensors, a sensor configured according to certainembodiments may provide a two dimensional grid that is capable ofcapturing multiple pixels of information from an object by activatingindividual pairs of drive and pickup lines and capturing the resultantsignal. This signal can be processed with logic or processor circuitryto define features and/or characteristics of an object. For example, theinformation may be used to produce renderings of an object, such as afingerprint, and compare the renderings to secured information forauthentication.

According to one embodiment, and in contrast to conventional approaches,a device can utilize the intrinsic impedance sensing electrode pairformed at the crossings between the drive and pickup lines. Inoperation, the electric fields may be further focused by grounding driveand pickup lines near or about the area being sensed by the particularcrossover location at one time. This prevents interference that mayoccur if other drive and pickup lines were sensing electric fieldssimultaneously. More than one electrode pair may be sensedsimultaneously. However, where resolution is an important factor, it maybe preferred to avoid sensing electrode pairs that are too close to eachother to avoid interference and maintain accuracy in sensing objectfeatures at a particular resolution. For purposes of this description,“intrinsic electrode pair” refers to the use of the impedance sensingelectrode pairs that are formed at each of the drive and pickup linecrossover locations. Due to the fact that the embodiments use eachintrinsic electrode pair at each crossover as a sensing element, nodifferentiating geometric features exist at individual sensing nodes todistinguish them from the interconnect lines. As a result, the alignmentbetween the drive layers and sense layers is non-critical, whichsignificantly simplifies the manufacturing process.

Grounding the adjacent inactive drive and pickup lines restricts thepixel formed at each intrinsic electrode pair without requiring complexmeasures such as the dedicated guard rings employed in prior art (forexample U.S. Pat. No. 5,963,679). Instead, guard grounds around thepixel are formed dynamically by switching adjacent inactive drive andpickup lines into ground potential. This allows the formation of highdensity pixel fields with relatively low resolution manufacturingprocesses, as the minimum pixel pitch for a given process is identicalto the minimum feature spacing. This, in turn, enables the use of lowcost manufacturing process and materials, which is the key to creating alow cost placement sensor.

In one example, the sensor lines may consist of drive lines on one layerand pickup lines on another layer, where the layers are located overeach other in a manner that allows the separate sensor lines, the driveand pickup lines, to cross over each other to form impedance sensingelectrode pairs at each crossover location. These crossover locationsprovide individually focused electrical pickup locations or pixels, orelectrode pairs where a number of individual data points of featuresand/or characteristics of an object can be captured. The high degree offield focus is due to the small size of the intrinsic electrode pairs,as well as the high density of the neighboring ground provided by theinactive plates. The flexible substrate may have a second substrateconfigured with logic or processor circuitry for sending and receivingsignals with the sensor lines to electronically capture informationrelated to the object. Alternatively, there may be two separatesubstrates carrying the separate sensor lines and layered on each other,and yet connected to a third substrate for connection to logic orprocessor circuitry.

The utilization of the crossover locations between perpendicular lineson adjacent layers for the pickup cell greatly reduces the alignmentrequirements between the layers. Since there are no unique features at asensor pixel location to align, the only real alignment requirementbetween the layers is maintaining perpendicularity. If the sense celllocations had specific features, such as the parallel plate featurestypical of prior art fingerprint sensors, the alignment requirementswould include X and Y position tolerance of less than one quarter apixel size, which would translate to less than +/−12 um in each axis fora 500 DPI resolution fingerprint application.

In operation, a drive line is activated, with a current source forexample, and a pickup line is connected to a receiving circuit, such asan amplifier/buffer circuit, so that the resulting electric field can becaptured. An electric field extends from the drive line to the pickupline through the intermediate dielectric insulating layer. If an objectis present, some or all of the electric field may be absorbed by theobject, changing the manner in which the electric field is received bythe pickup line. This changes the resulting signal that is captured andprocessed by the pickup line and receiving circuit, and thus isindicative of the presence of an object, and the features andcharacteristics of the object may be sensed and identified by processingthe signal. This processing may be done by some form of logic orprocessing circuitry.

In other embodiments, the signal driving the drive line may be a complexsignal, may be a varying frequency and/or amplitude, or other signal.This would enable a sensor to analyze the features and/orcharacteristics of an object from different perspectives utilizing avarying or complex signal. The signal may include simultaneous signalsof different frequencies and/or amplitudes that would produce resultantsignals that vary in different manners after being partially or fullyabsorbed by the object, indicating different features andcharacteristics of the object. The signal may include different tones,signals configured as chirp ramps, and other signals. Processing orlogic circuitry may then be used to disseminate various information anddata points from the resultant signal.

In operation, the varying or complex signal may be applied to the driveline, and the pickup line would receive the resulting electric field tobe processed. Logic or processing circuitry may be configured to processthe resulting signal, such as separating out different frequencies ifsimultaneous signals are used, so that features and/or characteristicsof the object may be obtained from different perspectives.

Given the grid of pixels that can be activated at individual pairs, eachpixel may be captured in a number of ways. In one embodiment, a driveline may be activated, and pickup lines may be turned on and off in asequence to capture a line of pixels. This sequencing may operate as ascanning sequence. Here a first drive line is activated by connecting itto a signal source, and then one pickup line is connected toamplifier/buffer circuitry at a time, the information from the pixelformed at the crossing of the two lines is captured, and thendisconnected. Then, a next pixel is processed in sequence, then another,then another, until the entire array of pickup lines is processed. Thedrive line is then deactivated, and another drive line is activated, andthe pickup lines are again scanned with this active drive line. Thesemay be done one at a time in sequence, several non-adjacent pixels maybe processed simultaneously, or other variations are possible for agiven application. After the grid of pixels is processed, then arendering of object information will be possible.

Referring to FIG. 1, a diagrammatic view of one embodiment of a sensor100 configured according to one embodiment is illustrated. In thisconfiguration, pickup lines or top plates 102 a[m], 102 b[m+1] arelocated on a insulating dielectric substrate layer 104 and configured totransmit a signal into a surface of an object located in close proximityto the sensor lines. Drive lines or bottom plates 106 a[n], 106 b[n+1]are juxtaposed and substantially perpendicular to the drive lines orplates and are located on an opposite side of the a insulatingdielectric substrate to form a type of a grid. The pickup lines areconfigured to receive the transmitted electromagnetic fields modified bythe impedance characteristics on an object placed within the range ofthose electric fields.

Referring to FIG. 2, a diagrammatic view of a sensor 200 is shown havingpickup lines or top plates 202 a, 202 b and insulating layer 204, anddrive lines or bottom plates 206 a, 206 b. The Figure furtherillustrates how electromagnetic fields 208 a, 208 b extend between thedrive lines and pickup plates through the substrate. Without an objectwithin proximity, the electric field lines are uniform within the sensorstructure and between the different lines. When an object is present, aportion of the electric field lines are absorbed by the object and donot return to the pickup plates through the insulating layer.

Referring to FIG. 3, an object 310 is illustrated proximate the sensor300. The sensor 300 has pickup lines or top plates 302 a, 302 b, aninsulating dielectric layer 304, and drive lines or bottom plates 306 a,306 b. In operation, the drive lines and pickup lines of this deviceexample may be individually activated, where a drive line/pickup linepair is activated to produce an active circuit. The result is a circuitthat transmits electric field from active drive plate 316 into thecombined dielectric of the insulating layer 304 and object 310 viaelectric field lines, 306 a, 306 b, and received by the active pickupplate. As the illustration shows, some of the field lines are capturedby the object when it is placed about the active electrode pair. Thevariations in an object, such as peaks and valleys and other features ofan object surface, can be detected and captured electronically bycapturing and recording the resulting electric field variationsoccurring at different crossover locations of the drive and pickuplines. Similar to common capacitance based placement sensors, the sensorcan capture a type of image of the object surface electronically, andgenerate a representation of the features and characteristics of anobject, such as the features and characteristics of a fingerprint in thefingerprint sensor example described below.

In this configuration of FIG. 3, only one active electrode pair isillustrated. However, the embodiment is not limited to this particularconfiguration, where one single electrode pair, several electrode pairs,or even all electrode pairs may be active at one time for differentoperations. In practice, it may be desirable for less than all of theelectrode pairs to be active at a given time, so that any interferencethat may occur between close-by pixels would be minimized. In oneembodiment, a drive line may be activated, and the pickup lines may bescanned one or more at a time so that a line of pixels can be capturedalong the drive line and pickup lines as they are paired along a line atthe crossover locations. This is discussed in more detail below inconnection with FIG. 5.

In general, in operation, each area over which a particular drive lineoverlaps a pickup line with a separation of the a insulating dielectricsubstrate is an area that can capture and establish a sensing locationthat defines characteristics or features of a nearby object about thatarea. Since there exist multiple sensing locations over the area of thesensor grid, multiple data points defining features or characteristicsof a nearby object can be captured by the sensor configuration. Thus,the sensor can operate as a planar two-dimensional sensor, where objectslocated on or about the sensor can be detected and their features andcharacteristics determined.

As described in the embodiments and examples below, the embodiment isnot limited to any particular configuration or orientation described,but is only limited to the appended claims, their equivalents, and alsofuture claims submitted in this and related applications and theirequivalents. Also, many configurations, dimensions, geometries, andother features and physical and operational characteristics of anyparticular embodiment or example may vary in different applicationswithout departing from the spirit and scope of the embodiment, which,again, are defined by the appended claims, their equivalents, and alsofuture claims submitted in this and related applications and theirequivalents.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the embodiment. However, itwill be apparent to one skilled in the art that the embodiment can bepracticed without these specific details. In other instances, well knowncircuits, components, algorithms, and processes have not been shown indetail or have been illustrated in schematic or block diagram form inorder not to obscure the embodiment in unnecessary detail. Additionally,for the most part, details concerning materials, tooling, processtiming, circuit layout, and die design have been omitted inasmuch assuch details are not considered necessary to obtain a completeunderstanding of the embodiment and are considered to be within theunderstanding of persons of ordinary skill in the relevant art. Certainterms are used throughout the following description and claims to referto particular system components. As one skilled in the art willappreciate, components may be referred to by different names. Thisdocument does not intend to distinguish between components that differin name, but not function. In the following discussion and in theclaims, the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . ”

Embodiments of the embodiment are described herein. Those of ordinaryskill in the art will realize that the following detailed description ofthe embodiment is illustrative only and is not intended to be in any waylimiting. Other embodiments of the embodiment will readily suggestthemselves to such skilled persons having the benefit of thisdisclosure. Reference will be made in detail to implementations of theembodiment as illustrated in the accompanying drawings. The samereference indicators will be used throughout the drawings and thefollowing detailed description to refer to the same or like parts.

In the interest of clarity, not all of the routine features of theimplementations described herein are shown and described. It will, ofcourse, be appreciated that in the development of any such actualimplementation, numerous implementation-specific decisions must be madein order to achieve the developer's specific goals. Moreover, it will beappreciated that such a development effort might be complex andtime-consuming, but would nevertheless be a routine undertaking ofengineering for those of ordinary skill in the art having the benefit ofthis disclosure.

In one embodiment, a sensor device includes drive lines located on orabout an insulating dielectric substrate and configured to transmit asignal onto a surface of an object being sensed. Pickup lines arelocated near or about the drive lines and configured to receive thetransmitted signal from the surface of an object. In order to keep aseparation between the drive lines and pickup lines, the substrate mayact as an insulating dielectric or spacing layer. The substrate may befor example a flexible polymer based substrate. One example is Kapton™tape, which is widely used in flexible circuits such as those used inprinter cartridges and other devices. The package may include such aflexible substrate, where the drive lines may be located on one side ofthe substrate, and the pickup lines may be located on an opposite sideof the substrate.

The drive lines may be orthogonal in direction with respect to thepickup lines, and may be substantially perpendicular to the pickuplines. According to one embodiment, a device may be configured withdrive lines and pickup lines located on or about opposite sides of aninsulating dielectric substrate, where the combination of these threecomponents provides capacitive properties. The drive lines may beactivated to drive an electric field onto, into or about an object. Thepickup lines can receive electronic fields that originated from thedrive lines, and these electronic fields can be interpreted byprocessing or logic circuitry to interpret features or characteristicsof the object being sensed.

Thus, in one embodiment the layer separating the drive lines from thepickup lines can provide a capacitive property to the assembly. If someor all of the drive lines are substantially perpendicular to the pickuplines, either entirely or in portions, then a grid may be formed. Insuch a configuration, from a three dimensional view, the drive lines arelocated and oriented substantially in parallel with respect to eachother about a first plane. One surface of the substrate is located aboutthe drive lines in a second plane that is substantially parallelrelative to the drive lines. The pickup lines are located and orientedsubstantially in parallel with respect to each other about a third planethat is substantially parallel to the first and second planes and alsolocated about another substrate surface that is opposite that of thedrive lines, such that the substrate is located substantially betweenthe drive lines and the pickup lines.

In this description, including descriptions of embodiments and examples,there will be references to the terms parallel, perpendicular,orthogonal and related terms and description. It is not intended, norwould it be understood by those skilled in the art that thesedescriptions are at all limiting. To the contrary, the embodimentextends to orientations and configurations of the drive lines, thepickup lines, the substrate or related structure, and also variouscombinations and permutations of components, their placement, distancefrom each other, and order in different assemblies of a sensor. Thoughthe embodiment is directed to a sensor configured with plurality ofdrive and pickup lines that generally cross over each other at a pixellocation and are configured to detect presence and other features andcharacteristics of a nearby object, the embodiment is not limited to anyparticular configuration or orientation, but is only limited to theappended claims, their equivalents, and also future claims submitted inthis and related applications and their equivalents.

Also, reference will be made to different orientations of the geometricplanes on which various components will lie, such as the drive andpickup lines and the substrate that may be placed in between the sets ofdrive and pickup lines. If flexible substrates are used for example, theuse of such a structure will allow for planes to change as a flexiblestructure is flexed or otherwise formed or configured. In suchembodiment will be understood that certain aspects of the embodiment aredirected to the drive lines and pickup lines being configured onopposite sides of a substrate and in a manner that enables the sensingof particular features and/or characteristics of a nearby object at eachcrossover location of a drive line and a pickup line. Thus, theorientation of the planes (which may be deformable, and thus may besheets separated by a substantially uniform distance) of groups ofcomponents (such as drive lines or pickup lines for example) orsubstrates may vary in different applications without departing from thespirit and scope of the embodiment.

Also, reference will be made to pickup lines, pickup plates, drivelines, drive plate, and the like, but it will be understood that thevarious references to lines or plates may be used interchangeably and donot limit the embodiment to any particular form, geometry,cross-sectional shape, varying diameter or cross-sectional dimensions,length, width, height, depth, or other physical dimension of suchcomponents. Also, more sophisticated components may be implemented toimprove the performance of a device configured according to theembodiment, such as for example small 65, 45, 32 or 22 nanometerconduction lines or carbon nano-tubes that may make an assembly moreeasily adapted to applications where small size and shape as well as lowpower are desired characteristics and features. Those skilled in the artwill understand that such dimensions can vary in different applications,and even possibly improve the performance or lower power consumption insome applications, without departing from the spirit and scope of theembodiment.

Reference will also be made to various components that are juxtaposed,layered, or otherwise placed on each other. In one example of anembodiment, a plurality of drive lines are juxtaposed on one surface ofa generally planar substrate, and a plurality of pickup lines arejuxtaposed on an opposite surface of the planar substrate. The drivelines are substantially orthogonal to the pickup lines, and may bedescribed as substantially perpendicular to the pickup lines. Thedistance between the drive lines and pickup lines may be filled with asubstrate or insulating material that will provide for a capacitiveconfiguration. Here the drive lines on one side of the substrate formsone capacitive plate, and the pickup lines on an opposite side for thecorresponding capacitive plate. In operation, when the drive plate isactivated, an electrical field is generated between the drive lines andpickup lines and through the substrate to form a plurality of capacitiveelements. These capacitive elements are located at an area at eachcross-section of a drive line and a pickup line with a portion of thesubstrate located between the areas. This is a location where therespective drive lines and pickup lines overlap each other. In anyparticular application, these areas in which the three componentsinteract during operation define a data location at which a sensorreading can be made.

Reference will also be made to sensor lines, such as sensor drive linesand sensor pickup lines, and their orientation amongst themselves andeach other. For example, there will be described substantially paralleldrive lines. These drive lines are intended to be described as parallelconductive lines made up of a conductive material formed, etched,deposited or printed onto the surface such as copper, tin, silver andgold. Those skilled in the art will understand that, with the inherentimperfections in most any manufacturing process, such conductive linesare seldom “perfect” in nature, and are thus not exactly parallel inpractice. Therefore, they are described as “substantially parallel”.Different applications may configure some of the drive lines evennon-parallel, such that the lines may occur parallel for a portion ofthe line, and the line may necessarily deviate from parallel in order toconnect with other components for the device to operate, or in order tobe routed on or about the substrate on which it is formed or traced.Similarly, the separate array of lines may be described as orthogonal orperpendicular, where the drive lines are substantially orthogonal orperpendicular to the pickup lines. Those skilled in the art willunderstand that the various lines may not be perfectly perpendicular toeach other, and they may be configured to be off-perpendicular orotherwise crossed-over in different angles in particular applications.They also may be partially perpendicular, where portions of drive linesmay be substantially perpendicular to corresponding portions of pickuplines, and other portions of the different lines may deviate fromperpendicular in order to be routed on or about the substrate or to beconnected to other components for the device to operate.

These and other benefits provided by the embodiment will be described inconnection with particular examples of embodiments of the embodiment andalso descriptions of intended operational features and characteristicsof devices and systems configured according to the embodiment.

In operation, generally, the drive lines can transmit an electromagneticfield toward an object that is proximal to the device. The pickup linesmay receive a signal originating from the drive lines and thentransmitted through the object and through the substrate and onto thepickup lines. The pickup lines may alternatively receive a signaloriginating from the drive lines that were then transmitted through thesubstrate and onto the pickup lines without passing through the object.This electric field can vary at different locations on the grid, givinga resultant signal that can be interpreted by some type of logic orprocessor circuitry to define features and/or characteristics of anobject that is proximate the assembly.

The drive lines and pickup lines may be controlled by one or moreprocessors to enable the transmission of the signal to an object via thedrive lines, to receive a resultant signal from an object via the pickuplines, and to process the resultant signal to define an object image.One or more processors may be connected in one monolithic component,where the drive lines and pickup lines are incorporated in a packagethat includes the processor. In another embodiment, the drive lines,pickup lines and substrate may be assembled in a package by itself,where the package can be connected to a system processor that controlsgeneral system functions. This way, the package can be made part of thesystem by connecting with a system's input/output connections in orderto communicate with the system. This would be similar in nature forexample to a microphone connected to a laptop, where the audio signalsare received by the system processor for use by the laptop in receivingsounds from a user. According to this embodiment, the sensor can beconnected as a stand-alone component that communicates with the systemprocessor to perform sensor operations in concert with the systemprocessor.

In another embodiment, a sensor may be configured to drive signals atdifferent frequencies since the impedance of most objects, especiallyhuman tissue and organs, will greatly vary with frequency. In order tomeasure complex impedance at one or more frequencies of a sensed object,the receiver must be able also to measure phase as well as amplitude. Inone embodiment, the resulting signal generated from a given impedancesensing electrode pair may result from varying frequencies, known in theart as frequency hoping, where the receiver is designed to track arandom, pseudo-random or non-random sequence of frequencies. A variationof this embodiment could be a linear or non-linear frequency sweep knownas a chirp. In such an embodiment one could measure the impedance of acontinuous range frequencies very efficiently.

In yet another embodiment, a grid sensor as described above may beconfigured to also operate as a pointing device. Such a device couldperform such functions as well known touch pads, track balls or miceused in desktops and laptop computers.

In one example of this embodiment, a two dimensional impedance sensorthat can measure the ridges and valleys of a finger tip may beconfigured to track the motion of the fingerprint patterns. Prior artswiped fingerprint sensors can perform this function, but due to thephysical asymmetry of the array and the need to speed correct, or“reconstruct” the image in real time make these implementations awkwardat best. The sensor could also double as both a fingerprint sensor and ahigh quality pointing device.

One device configured according to the embodiment includes a first arrayof sensor lines on a flexible substrate, and a second array of sensorlines on a flexible substrate, and also a processor configured toprocess fingerprint data from the first and second arrays of sensorlines. When folded upon itself in the case of a single flexiblesubstrate or when juxtaposed in the case of separate substrates, theseparate sensor lines cross each other without electrically shorting toform a grid with cross-over locations that act as pixels from whichfingerprint features can be sensed. In one embodiment, an array ofsubstantially parallel sensor drive lines is located on a surface of theflexible substrate. These drive lines are configured to sequentiallytransmit signal into a surface of a user's finger activating a line at atime. A second array of sensor lines is similar to the first, consistingof substantially parallel sensor pickup lines that are substantiallyperpendicular to the drive lines. These pickup lines are configured topick up the signal transmitted from the first.

In the configuration where the first and second set of sensor lines, thedrive and the pickup lines for example, are located on differentsections of an extended surface of the flexible substrate, the flexiblesubstrate is further configured to be folded onto itself to form a duallayer configuration. Here, the first array of sensor drive lines becomessubstantially perpendicular to the second array of pickup sensor lineswhen the flexible substrate is folded onto itself. This folding processcreates crossover locations between these separate arrays of sensorlines—though they must not make direct electrical contact so that theyoperate independently. These crossover locations represent impedancesensing electrode pairs configured to sense pixels of an object and itssub-features juxtaposed relative to a surface of the flexible substrate.The scanning of these pixels is accomplished by activating individualrows and columns sequentially. Once a drive column is activated withdrive signal the perpendicular pickup rows are scanned one at a timeover the entire length of the selected driver. Only one row iselectrically active (high impedance) at a time, the non active rows areeither shorted to ground or multiplexed to a state where they do notcross couple signal. When a finger ridge is placed above an arraycrossover location that is active, it interrupts a portion of theelectric field that otherwise would be radiated through the surface filmfrom the active drive column to the selected row pickup. The placementof an object's subfeature, such as a ridge or valley in the case of afingerprint sensor, over an impedance sensing electrode pair results ina net signal decrease since some of the electric field is conducted toground through the human body. In a case of a fingerprint sensor theplacement of a fingerprint ridge/valley over an impedance sensingelectrode pair, the valley affects the radiation of electric field fromthe selected drive line to the selected pickup line much less than aridge would. By comparing the relative intensity of signals between thepixels ridges and valleys, a two dimensional image of a finger surfacecan be created.

Referring again to FIG. 1, this general example of the grid sensor willbe now used to illustrate how such a sensor configured according to theembodiment can be implemented as a fingerprint sensor, where the objectwould simply be the surface of the fingerprint on the user's finger.This example will be carried through the following Figures forillustration of the benefits and novel features of the impedance sensorconfigured according to the embodiment. However, it will be appreciatedby those skilled in the art, however, that any object may be sensed by adevice configured according to the embodiment. Again, the example anddescription are intended only for illustration purposes.

In operation, the sensor can be configured to detect the presence of afinger surface located proximate to the sensor surface, where the drivelines can drive an active electromagnetic field onto the finger surface,and the pickup lines can receive a resulting electromagnetic fieldsignal from the pickup lines. In operation, the drive lines can generatean electric field that is passed onto the surface of the finger, and thedifferent features of the fingerprint, such as ridges and valleys of thefingerprint surface and possibly human skin characteristics, would causethe resulting signal to change, providing a basis to interpret thesignals to produce information related to the fingerprint features.

In one embodiment of a fingerprint sensor, referring again to FIG. 1 inthe context of a fingerprint sensor, a flexible substrate is used as theinsulating dielectric layer 104, to allow for beneficial properties ofdurability, low cost, and flexibility. The drive lines or plates 106 a,106 b, are located on the flexible substrate and configured to transmita signal into a surface of a user's fingerprint features and structures,such as ridges and valleys, placed on or about the sensor lines. Thepickup lines 102 a, 102 b are configured to receive the transmittedsignal from the user's finger surface. A processor (not shown) can beconfigured to collect and store a fingerprint image based on thereceived signal from the pickup lines.

Referring to FIG. 4, an example a sensor 400 configured as an objectsensor, where the top plates or pickup lines 402 a, 402 b, . . . , 402 nare located on one side of insulating dielectric layer or substrate 404.Bottom plates or pickup lines 406 a, 406 b, . . . , 406 n are located onan opposite side of the substrate 404. Electric fields 408 a, 408 bextend from bottom plates or drive lines 406 a, 406 b through theinsulating layer or substrate 404 and onto active top plate 402 a.According to the embodiment, these drive lines may be activated one at atime to reduce any interference effects, but the electric field resultsillustrated here are intended to illustrate a contrast between electricfields that are partially or fully absorbed by the object with electricfields that are not absorbed the object at all. This information may becollected from drive and pickup plate electrode pairs at each crossoverlocation to sense features and characteristics of the object that isproximate the sensor lines. Partially covered top plate or pickup line402 b is connected to voltmeter 417, and uncovered top plate 402 a isconnected to voltmeter 418. Active drive line or bottom plate 406 b isconnected is connected to AC signal source 416, causing an electricfield to radiate from active plate 406 b. According to a particularapplication, the number of drive lines and pickup lines can varydepending on the application, and it may depend on the cost andresolution desired. As can be seen, the electric field lines 408 a ispartially captured by the pickup lines 402 a and 402 b, and part iscaptured by the object, in this case finger 410. Also, in order toillustrate that the pickup lines will exhibit different reading when anobject or object feature is present or not present or proximate to agiven crossover location, volt meter 417 illustrates the response to thetop plate or drive line 402 b, and voltmeter 418 illustrates theresponse of top plate or drive line 402 a. The difference in thedeflections of voltmeter 417 in comparison 418 show the delta inelectric field intensity between the two electrode pair locations, onewith a finger present the other without.

Referring to FIG. 5, another example of a sensor configured according tothe embodiment is illustrated the Drive and pickup configuration whendetecting the presence of an object. The sensor 500 is illustrated,where the top plates or pickup lines 502 a, 502 b, . . . , 502 n arelocated on one side of insulating layer or substrate 504, and bottomplates or drive lines 506 a, 506 b, . . . , 506 n are located on anopposite side of the substrate 504. Again, the pickup lines are shown onthe layer closest to the object being sensed for maximum sensitivity,and the drive lines shown on the opposite side of the substrate.Electric fields 508 a, 508 b extend from bottom plates or drive lines506 a, 506 b through the insulating layer or substrate 504 and ontoactive top plate 502 b. Other configurations are possible, perhapshaving drive plates on the top, and pickup plates on the bottom. Theembodiment, however, is not limited to any particular configuration thatis insubstantially different than the examples and embodiments disclosedand claimed herein.

FIG. 5, further shows a snapshot of one selected individual electrodepair located at the crossover of pickup line 502 b and drive line 506 b,where the remaining pickup and drive lines are not active, showngrounded in FIG. 5. Drive line 506 b is connected to AC voltage source516, and pickup line 502 b is connected to amplifier/buffer 514. Onceactivated as shown here, electric field lines 508 a, 508 b aregenerated, and they radiate from drive line 506 b and are sensed bypickup line 502 b, sending the resultant signal into amplifier/buffer514, and are later processed by analog and digital circuit functions.Grounding the inactive adjacent drive and pickup lines focuses theelectric fields 508 a and 508 b at the crossover location between theactive the drive and pickup plates, limiting crosstalk from adjacentareas on the object being sensed. As the sensing operation proceeds inthis embodiment, different drive line/pickup line crossover pairings maybe activated to capture different pixels of information from the object.In the case of an object sensor, it can capture information on the shapeof the object, and, if the electrical characteristics are non-uniformacross its surface, it's composition. Again, the embodiment is notlimited to this particular configuration, where one single electrodepair, several electrode pairs, or even all electrode pairs may be activeat one time for different operations. In practice, it may be preferablefor less than all of the impedance sensing electrode pairs to be activeat a given time, so that any interference that may occur betweenclose-by pixels would be minimized. In one embodiment, a drive line maybe activated, and the pickup lines may be scanned one or more at a timeso that a line of pixels can be captured along the drive line and pickuplines as they are paired along a line at the crossover locations. Thus,and still referring to FIG. 5, the AC voltage source 516 may remainconnected to drive line 506 b, and the connection of theamplifier/buffer 516 may cycle or scan over to sequential pickup lines,so that another pixel of information can be captured from another pickupline crossover paired with drive line 506 b. Once substantially all thepickup lines 506 a-n have been scanned drive line 506 b can bedeactivated, than another drive line in sequence can be activated withthe AC voltage source, and a new scanning can commence through thepickup lines. Once substantially all drive line/pickup line pairingshave been scanned to capture the full two-dimensional array of pixels,then a two dimensional image or rendering of the object features andcharacteristics can be made, such as a rendering of the shape of theobject, and potentially a composition map.

As another example of a sensor that can benefit from the embodiment, areduced cost fingerprint swipe sensor could be configured using the sameinnovation provided by the embodiment. In this embodiment, a reducednumber of pickup lines could be configured with a full number oforthogonal drive lines. Such a configuration would create a multi-lineswipe sensor that would take the form of pseudo two-dimensional sensor,and when a finger was swiped over it would create a mosaic of partialimages or slices. The benefit of this would be to reduce the complexityof image reconstruction task, which is problematic for currentnon-contact silicon sensors that rely on one full image line and asecond partial one to do speed detection.

The tradeoff would be that this pseudo two dimensional array would haveto be scanned at a much faster rate in order to keep up with the varyingswipe speeds of fingers that have to be swiped across it.

FIGS. 6 a and 6 b illustrate the operation of the sensor when detectingsurface features of an object such as fingerprint ridges and valleys.The sensor is configured identically to the previous example in FIG. 5,but in this case is interacting with a textured surface such as afingerprint.

Referring to FIGS. 6 a and b, another example of a sensor configuredaccording to the embodiment is illustrated. The sensor 600 isillustrated, where the top plates or pickup lines 602 a-n are located onone side of insulating layer or substrate 604, and bottom plates ordrive lines 606 a-n are located on an opposite side of the substrate604. For maximum sensitivity pickup lines are shown on the layer closestto the object being sensed, and the drive lines shown on the oppositeside of the substrate. FIG. 6 a shows electric field lines 620 as theyinteract with a proximally located object's valley and FIG. 6 b showselectric field lines 621 as the interact with a proximally locatedobject's peaks, extending from bottom plate drive line 606 b through theinsulating layer or substrate 604 and onto active drive line 606 b. Inthe case of sensing a fingerprint, the corresponding ridges and valleysover the fingerprint surface can be captured by the grid of driveline/pickup line crossover points, and the resulting data can be used torender an image of the fingerprint. A stored fingerprint can then becompared to the captured fingerprint, and they can be compared forauthentication. This is accomplished using any one of many fingerprintmatching algorithms which are available from vendors as stand aloneproducts. Such vendors include Digital Persona, BioKey, and CogentSystems, to name just a few.

Also illustrated in FIGS. 6 a and b, is the individual sensor linepairing of pickup line 602 b and drive line 606 b. Their crossover formsthe active electrode pair, and the remaining pickup and drive lines arenot active, and will nominally be grounded by electronic switches. Driveline 606 b is connected to AC voltage source 616, and pickup line 602 bis connected to amplifier/buffer 605. Once activated as shown here,electric field lines 620 and 621 are created as shown in FIGS. 6 a and 6b respectively, and they emanate between the drive line 606 b and pickupline 602 b, sending a resultant signal that is radiated onto pickup line602 b and connected to amplifier/buffer 605, and later processed byanalog and digital processing circuitry. As the sensing operationproceeds in this embodiment, different drive line/pickup line crossoverpairs may be activated to capture different pixels of information fromthe object. In the case of a fingerprint, it can capture information ondifferent features and characteristics of the fingerprint and even thebody of the finger itself. Again, the embodiment is not limited to thisparticular configuration, where one electrode pair, several electrodepairs, or even all electrode pairs may be active at one time fordifferent operations. In practice, it may be preferable for less thanall of the electrode pairs to be active at a given time, so that anyinterference that may occur between close-by pixels would be minimized.In one embodiment, a drive line may be activated, and the pickup linesmay be scanned one or more at a time so that a line of pixels can becaptured along the drive line and pickup lines as they are paired alonga line at the crossover points. Thus, and still referring to FIG. 6 a,the voltage source 616 may remain connected to drive line 606 b, and theconnection to buffer/amplifier 605 may cycle or scan over to anotherpickup line, so that another pixel of information can be captured fromanother electrode pair using driveline 606 b.

In the snapshot shown in FIGS. 6 a and 6 b drive plate 606 b remainsexcited by AC signal source 616 until an entire column of pixels isscanned, while unused drive plates (606 a,c-n etc.), are switched toground for isolation purposes. Likewise, in one embodiment only onepickup plate is active at a time and some or substantially all otherpickup plates are switched to ground to minimize crosstalk.

The scanning process continues beyond the snapshot shown in FIGS. 6 aand 6 b, with the next column in sequence being activated, 606 c,(although the sequence could be arbitrary), Once the entire sequence ofPickup Plates 602 a-n is scanned, the next driver line 606 d wouldactivated, until all, or substantially all of the drive lines 606 a-nhave been sequenced. Once all the drive columns have been activated andthe pickup plates scanned for each column, one will have collected acomplete two dimensional array of pixels equal to the number of driverrows times the number of pickup columns. For a 500 DPI sensor that wouldcreate a 10×10 mm array or 100 mm², consisting of 40,000 individualpixels. Depending on the application, all of the drive lines may besequenced, or possibly some or most of them may be sequenced.

Referring again to FIGS. 6 a and 6 b, the two conductive layers Drivelayer 606 and Pickup layer 602, are separated by an electricallyinsulating layer 604. This insulating layer 604 has high DC resistanceand has a dielectric constant greater than one to allow the transmissionof high frequency electric fields through it. In one embodiment thislayer 602 is created by folding a single sided flexible printed circuitboard back onto itself. In another embodiment it is created by placing adielectric layer between two electrically active layers to form a doublesided circuit board.

FIG. 7 shows an example of an x-y grid of plate rows and columnsdepicted by lumped circuit components that represent the electric fieldcouplings of the sensor at each drive/pickup crossover.

The bottom plates 701 a,b,c etc. are driven one at a time by AC signalsource 716 via switch matrix 740 a-n. FIG. 7 shows a scan snapshot whereone drive switch 740 b in the on condition connecting the correspondingplate to the signal source. This activates one entire row 740 b with ACsignal over the entire length of the plate that is equal to the sensorwidth in one dimension. Correspondingly each column plate 703 a,b,c etc.will pickup up AC signal through insulating layer 704 and couplingcapacitors 761 a,b,c . . . n. Only one pickup plate at a time is activebeing switched into the buffer amplifier 716. Top Plate 702 b is shownas the active plate in FIG. 7, while all or substantially all otherpickups are shorted to ground via switch matrix 730 a-n, thus theinformation from one x-y pixel is captured.

A single row remains active only as long as it takes the entire numberof pickup plates/columns to be scanned. Scan time per pixel will dependon the frequency of operation and the settling time of the detectionelectronics, but there is no need to scan unduly fast as is typical withprior art swipe sensors. On the other hand prior art swipe sensors mustscan at a very high pixel rate in order not to lose information due toundersampling relative to the finger speed that can be greater than 20cm/sec. This reduction in capture speed relative to a swipe sensorrelaxes the requirements of the analog electronics and greatly reducesthe data rate that a host processor must capture in real time. This notonly reduces system cost but allows operation by a host device with muchless CPU power and memory. This is critical especially for mobiledevices.

Once an entire row 706 b has been scanned by all or substantially all ofits corresponding pickup plates 702 a-n, then the next row in thesequence is activated through switch matrix 740. This process continuesuntil all or substantially all of the rows and columns are scanned.

The amount of signal that is coupled into the buffer amplifier 716 is afunction of how much capacitance is formed by the insulating layer andthe finger ridge or valley in close proximity. The detailed operation ofhow these electric fields radiate is shown in Figures 6 a and b. Thetotal coupling capacitance is a series combination of the insulatinglayer capacitance 704 that is fixed for a given thickness, and thevariable topological capacitance of the object being sensed. Thevariable portion of this is shown in FIG. 7 as a series of variablecapacitors numbered 760 a-n, 761 a-n, 762 a-n etc., forming a twodimensional array.

FIG. 8 shows an example of an embodiment of the placement sensor using adifferential amplifier 880 to take the signal from the selected pickupplate (802 a-n), and subtract it from the reference signal of plate 805.The electrical subtraction of these signals performs several functions:first wide band common mode is subtracted out; second, subtractingagainst reference plate 805 provides a relative reference signalequivalent to an ideal ridge valley; third, common mode carrier signalthat couples into both plates other than through a finger is alsosubtracted out. First order carrier cancellation of etch variation inthe pickup plates also occurs when we subtract out carrier that iscoupled in by other means than through fingers placed on the sensor.This is critical for high volume manufacturing at a low cost.

Reference plate 805 is intentionally located outside of the fingercontact area of the sensor, separated from pickup plates 802 a-n by Gap885, Gap 885 is much larger that the nominal gap between the pickupplates that is typically 50 um. In a real world embodiment plate 805would be positioned under the plastic of a bezel to prevent fingercontact, placing it at least 500 um apart from the other pickup plates.

Each one of the pickup plates 802 a-n is scanned sequentially beingswitched through pickup switches 830 a-n connecting them to DifferentialAmplifier 880. During the scanning process of an entire pickup row, thepositive leg of the differential amplifier remains connected toreference plate 805 to provide the same signal reference for all of thepickup plates.

FIG. 9 a shows a circuit diagram of an example of a front end for theplacement sensor in a topology that uses a bank of Single Pole DoubleThrow Switches or SPDTs to scan the pickup plate rows and a bank ofSingle Pole Single Throw switches to multiplex the pickup plate columns.

In FIG. 9 a we see a snapshot of the analog switches as the scanningprocess begins. Only the first SPDT switch 1044 a is shown in the “on”position, which allows pickup plate 902 a to conduct its plate signalinto Differential Amplifier 980. The remaining pickup plates are shortedto ground via switches 944 a-944 n, preventing any pickup signalreceived by them from entering into differential amplifier 980.

Each SPDT has a Parasitic Capacitance 945, due to the fact that realworld switches to not give perfect isolation. In fact the amount ofisolation decreases with frequency, typically modeled by a parallelcapacitor across the switch poles. By using a SPDT switch we can shuntthis capacitance to ground when an individual plate is not active. Sincethere is a large array of switches equal to the number of pickup plates,typically 200 for a 500 dpi sensor, the effective shunt capacitance toground is multiplied by that number. So if a given switch has 0.5picofarads of parasitic capacitance and there where 200 pickups, thatwould add up to 100 picofarads of total shunt capacitance.

In order to prevent this large capacitance from diverting most of thereceived signal from the active pickup to ground, it is desirable inthis example to use a compensating circuit. This is accomplished byusing resonating inductor 939, forming a classic bandpass filter circuitin conjunction with parasitic capacitors 945 (one per switch) and tuningcapacitors 934 and 937. A two step null & peak tuning calibrationprocedure is used where tuning capacitor 934 and 937 are individuallytuned with inductor 939 using the same drive signal on both the plus andminus inputs to differential amplifier 980. The two bandpass filtersformed with inductor 1039 and resonating capacitors 934, and 937respectively, will be tuned to the same center frequency when there iszero signal out of differential amplifier 980. Next capacitors 934 and937 and inductor 939 are tuned together using a differential inputsignal with opposite 180 degrees phases on the plus and minus inputs tothe differential amplifier 980. They are incremented in lock step untilthe exact drive carrier frequency is reached, this occurs when theoutput of differential amplifier 980 is at its peak, making the centerfrequency equal to the exact frequency of the carrier drive signal 916.

In a systems implementation, a calibration routine would be performedbefore each fingerprint scan to minimize drift of this filter with timeand temperature. The resonating inductor 939 needs to have a Q orQuality Factor of at least 10 to give the filter the proper bandwidthcharacteristics necessary to optimize the signal to noise ratio.

Alternately, carrier source 916 may be a variable frequency source, andcapicitors (937 and 934) may be fixed values. In this embodiment, tuningis accomplished by varying the frequency of source 916) until peakoutput is obtained from differential amplifier 980

FIG. 9 b shows an alternate example of a device employing multiple banksof plates grouped together, each with their own differential amplifiers.

Dividing up the large number of parallel pickup plates into groups eachcontaining a smaller number of plates is an alternate architecture thatwould not require the use of a tuned bandpass filter in the front endbecause the parasitic switch capacitances would be greatly reduced. Thiswould have two possible advantages, first lower cost, and second theability to have a frequency agile front end. In this Figure we have asnapshot of the front end where the first switch 944 a of bank 907 a isactive. All other switch banks 907 a-907 n are shown inactive, shortingtheir respective plates to ground. Therefore, only voltage or currentdifferential amplifier 980 a has any plate signal conducted into it,voltage or current differential amplifiers 980 b-980 n have both theirpositive and negative inputs shorted to ground through their respectiveswitches 945 a-n and 945 r, preventing any signal from those banksmaking a contribution to the overall output.

Each of the differential amplifiers 980 a-980 n is summed throughresistors 987 a-987 n into summing amplifier 985. Only the differentialamplifier 980 a in this snapshot has plate signal routed into it, so itindependently produces signal to the input of summing amplifier 985.This process is repeated sequentially until all or substantially all ofthe switch banks 907 a-n, and switch plates 944 a-n, 945 a-n, etc, ofthe entire array are fully scanned. In different embodiments, all orsubstantially all of the array may be scanned, or less than the entirearray may be scanned in different applications. In some applications, alower resolution may be desired, so all of the array may not need to bescanned. In other applications, a full image may not be necessary, suchas a navigation application, where limited images may be used to detectmovement of speed, distance and/or direction to use as input for apointing device, such as directing a cursor on a display similar to acomputer touch-pad or a mouse.

By splitting the pickup array up, the capacitive input load on eachplate is reduced from that of the full array of switches to the numberof switches within a given plate group. If we were to divide for example196 potential pickup plates into 14 banks of 14 plates, resulting in acapacitance load equal to the parasitic capacitance of 14 switches(944), plus the capacitive load of the differential amplifier. If analogswitches 944 are constructed with very low parasitic capacitance thenthe overall input load would be small enough not to need a bandpasscircuit in the front end in order to resonate out the load capacitance.As integrated circuit fabrication techniques improve we would be abledesign smaller switches with less parasitic capacitance, making thisapproach become more attractive.

FIG. 9 c illustrates another example of a front end circuit usingindividual plate buffers that are multiplexed into a second stagedifferential amplifier.

Buffers 982 a through 982 n as illustrated are special buffers that aredesigned to have very low input capacitance. In one embodiment, thesebuffers could be configured as single stage cascoded amplifiers in orderto minimize drain-to-gate Miller capacitance and die area. To bettermaximize plate to plate isolation, two sets of switches could be usedfor each input. Analog switches 930 a-930 n are included in this exampleto multiplex each selected buffer into differential amplifier 980.Switches 932 are included to shut down the power simultaneously to allthe other input buffers that are not selected. This effectively putsthem at ground potential. An alternate embodiment would be to put inputanalog switches in front of each amplifier to allow a short of theunused plates directly to ground. One effect of this approach may be anincrease in input load capacitance for each plate.

FIG. 9 c shows a snapshot of the scanning process where top plate 902 ais being sensed though buffer 982 a that has power supplied to itthrough switch 932 a. Analog switch 930 a is closed, routing it todifferential amplifier 980. All other buffer outputs are disconnectedfrom the differential amplifier 980 via analog switches 930 b-n andpower switches 982 b-n

The positive input to differential amplifier 980 is always connected tothe reference plate 902 r, providing an “air” signal reference to theamp. The differential amplifier 980 serves to subtract out noise andcommon mode carrier signal in addition to providing a “air” referencecarrier value.

FIG. 10 shows a particular embodiment of a placement sensor implementedwith traditional analog receiver technology. The analog front end beginswith Differential Amplifier 1080 where selected Pickup Plate 1002 a-n issubtracted from Reference Plate 1005, which is located outside thefinger contact area providing a reference signal equivalent to an idealfinger valley. A programmable gain stage or PGA 1090 follows theDifferential Amplifier 1090, but could be integrated into the same blockproviding both gain an subtraction in a single stage. PGA 1090 isdesigned to have a gain range wide enough to compensate for productionvariations in plate etching and solder mask thickness between thelayers.

Control processor 1030 orchestrates the scanning of the two dimensionalsensor plate array. Drive plates/columns 1002 a-1002 n are scannedsequentially by the Drive Plate Scanning Logic 1040 in the ControlProcessor 1030. When a selected drive plate is activated it is connectedto carrier signal source 1016. All inactive drive plates are connectedto ground. Before activating the next drive plate in the sequence theactive drive plate remains on long enough for the entire row of PickupPlates 1002 a-n to be scanned by Pickup Plate Logic 1045.

Analog mixer 1074 multiplies the gained up plate signal against thereference carrier 1013. The result is a classic spectrum of base bandplus harmonic products at multiples of the carrier frequency. An analoglow pass filter 1025 is employed to filter out the unwanted harmonicsand must have a sharp enough roll of to attenuate the informationassociated with of the second harmonic without losing base bandinformation.

Following the low pass filter is an A/D Converter 1074 that must sampleat a least twice the pixel rate to satisfy the Nyquist criteria. Memorybuffer 1032 stores the A/D samples locally with sufficient size to keepup with the worst case latency of the host controller. The A/D SampleControl Line 1078 provides a sample clock for the converter to acquirethe sequential pixel information that is created by the sequencing ofthe plate rows and columns.

FIG. 11 shows an example of one embodiment of a placement sensorimplemented with direct digital conversion receiver technology. In thisexample, the analog front end begins with Differential Amplifier 1180where selected Pickup Plate 1102 a-n is subtracted from Reference Plate1105, which is located outside the finger contact area providing areference signal equivalent to an ideal finger valley. The electricalsubtraction of these signals performs several functions: first wide bandcommon mode is subtracted out; second, subtracting against referenceplate 1105 provides a relative reference signal equivalent to an idealridge valley; third, common mode carrier signal that couples into bothplates other than through a finger is also subtracted out. Eliminationof common mode is particularly important in high RF noise environments.First order carrier cancellation of etch variation in the pickup platesalso occurs when we subtract out carrier that is coupled in by othermeans than through fingers placed on the sensor. This is critical forhigh volume manufacturing at a low cost.

A programmable gain stage or PGA 1190 follows the DifferentialAmplifier, which could easily be combined into a single differentialamplifier including programmable gain as is commonly done in modernintegrated circuit design PGA 1190 is designed to have a gain range wideenough to compensate for production variations in plate etching andsolder mask thickness between the layers.

Control processor 1130 orchestrates the scanning of the two dimensionalsensor plate array. Drive plates/columns 1102 a-1102 n are scannedsequentially by the Drive Plate Scanning Logic 1140 in the ControlProcessor 1130. When a selected drive plate is activated it is connectedto carrier signal source 1116. All inactive drive plates are connectedto ground. Before activating the next drive plate in the sequence theactive drive plate remains on long enough for the entire row of PickupPlates 1102 a-n to be scanned by Pickup Plate Logic 1145 and captured bythe A/D converter 1125.

The A/D Converter 1125 is sampled at a rate of at least twice thecarrier frequency to satisfy the Nyquist criteria. The A/D SampleControl Line 1107 provides a sample clock for the converter to acquirethe sequential pixel information that is created by the sequencing ofthe plate rows and columns.

Following the A/D converter is a Digital Mixer 1118 that digitallymultiplies the A/D output that is at the carrier frequency against thereference carrier generated by the Digitally Controlled Oscillator 1110.The result is that the signal is down converted to the base band withthe carrier removed. There are other unwanted spectral componentscreated by this process, namely a double time carrier side band, butthese can easily be filtered out.

A combination decimator and digital filter 1120 follows the DigitalMixer 1118. This block performs sampling down conversion, reducing thesample rate from at least twice the carrier frequency to at least twicethe pixel rate that is much lower. The digital filter would typicallyinclude a Cascaded Integrator Comb, or CIC filter, which removes theunwanted spectral byproducts of mixing as well as improving the receiversignal to noise. A CIC filter provides a highly efficient way to createa narrow passband filter after mixing the signal down to baseband withthe digital mixer. The CIC filter may be followed by a FIR filterrunning at the slower decimated rate to correct passband droop.

With a reduction of sample rate in the order of 100:1 a relatively smallControl Processor Buffer (1132) could be used to capture and entirefingerprint. For example a 200×200 array producing 40 k pixels could bestored in a 40 kb buffer. This is in contrast to a swipe sensor thatmust scan the partial image frames at a rate fast enough to keep up withthe fastest allowable swipe speed, usually around 200 ms. At the sametime, a slow swipe of two seconds must also be accommodated, requiringten times the amount of memory as the fastest one. Various techniqueshave been developed to throw away redundant sample lines before storage,but even with that the real time storage requirements are much greaterfor swipe sensors. This is a critical factor in Match on Chipapplications where memory capacity is limited. In addition, a placementsensor has no real-time data acquisition or processing requirements onthe host processor beyond the patience of the user for holding theirfinger in place.

Referring to FIG. 12A, and example of a sensor layout 1200 configuredaccording to one embodiment is illustrated in a configuration that isknown in the semiconductor industry as a Chip on Flex (CoF). Chip onFlex is a configuration where a processor chip is attached to a flexiblesubstrate, such as Kapton™ tape, and that is electrically connected toconductive lines and possibly other components located on the flexiblesubstrate. In this example, the sensor layout 1200 is shown within theborders of Kapton tape having pitch rails 1202, 1204 with slots 1206located along both rails. These slots are used in the manufacturingprocess to feed the tape through the process while lines and possiblycomponents are formed on the tape. The pitch of a device refers to thelength of Kapton tape required to form a device on the CoF. The distance“d” 1208, measured here between slots 1207 and 1209, is substantiallyconstant throughout each rail, and the pitch is a shorthand method ofdetermining the length of flex that a device covers. For the deviceshown in this example, the pitch 1212 shows a span between slot 1207 and1214 of eight slots, and thus would be characterized as an 8-pitchdevice. The example sensor device shown, which may be a fingerprintsensor or other type of placement, 2D or area sensor, illustrates anintegrated circuit 1210, which may be a logic circuit formed on asilicon substrate, a microprocessor, or other circuit for processingpixel information captured from a sensor circuit. The example may alsobe formed or otherwise manufactured on a substrate other than flexiblesubstrate or Kapton tape, in fact it may be formed on a siliconsubstrate, rigid board, or other substrate configured for variousapplications.

If configured as a fingerprint sensor or other placement sensor,integrated circuit 1210 may be a mixed signal chip that enables all orsome of the functions described in FIG. 16 below. In one embodiment, ithas enough inputs and outputs to drive a 200 by 200 line array of driveand pickup lines, and may have more or less of either lines. The toplayer 1220 is formed by an array of pickup lines connected directly tointegrated circuit 1210. This may be a flip chip mounted directly to theflex substrate without bond wires. In this example, the bottom layer isformed by folding the single layer back onto itself along the foldingaxis 1230 to create double layer active sensor area 1255. The drivelines fold to create the bottom layer 1225. The drive lines in thisexample are split into left and right groups 1240 and 1242 respectivelyfor the sake of layout balance, but could be all on the left or rightside of the sensing area. The left drive plate bundles 1240, and rightdrive plate bundles 1242 are inter-digitated with alternating left andright feeds to form a continuous line array on bottom layer 1225.

Flexible substrate based connector 1235 routes power, ground andinterface signals out to an external host or onto another substrate thatcontains system level components, such as those illustrated in FIG. 16and described below. These components may include but are not limited toa processor with memory, logic enabling imbedded matching algorithm(s)and encrypting/decrypting functions. In an alternative example,connector 1235 may be attached to the host substrate using conductiveadhesive otherwise known as anisotropic conductive film (ACF attach),which may be labeled as “high density” in some products.

Referring to FIG. 12B, another example of a sensor 1250 is shown havinga different orientation and configuration on a substrate. Similar to theabove example, the sensor 1250 is a placement sensor, and is configuredto be folded onto itself along the folding axis 1251 to create twolayers, the bottom layer 1252 with drive lines 1256, and top layer 1254,with pickup lines 1257, integrated circuit 1258, flex externalconnections 1262, and processor connections 1260 that may be used toconnect the integrated circuit to external devices, such as formanufacturing testing for example. This configuration, however, has amuch smaller pitch, again where the distance “d” is the distance betweeneach pair of slots 1206, and the pitch in this example is between slots1270 and 1272, making this device a 5-pitch device. This example devicetakes up 5 pitches of Kapton tape compared to the other example device1200 (FIG. 12A) taking up 8 pitches of Kapton tape. This device performssubstantially the same function as that of example 1200, FIG. 12A, yettakes up less Kapton tape, saving in material costs. The device may takeup even less pitches of tape if the size of the resulting sensor surfacewere reduced, allowing the space needed to accommodate the pickup lines,drive lines, and other components to be reduced. In this example, theeffective sensor surface may be ten square millimeters, and could bereduced to nine or even eight millimeters, and the structures could bereduced accordingly to reduce the overall area of the device, likewisereducing the area of substrate required to accommodate the overalldevice.

As will be appreciated by those skilled in the art, given theseexamples, different designs may be accomplished to optimize differentaspects of the invention, including size is the substrate used for adevice, and both the size and pixel density of the sensing area. Theinvention, however, is not limited to a particular optimization done byothers, and indeed the invention should inspire others to improve uponthe design using well known and alternative processes, materials, andknow-how available to them. The scope of the invention is only limitedby claims that are either appended or submitted for examination in thefuture, and not by information that is extemporaneous to thisspecification.

Referring to FIG. 13 a, an illustration of a flex layout structure 1300is illustrated. As shown, the flex layer structure 1300 includes animaging area 1350, in which drive lines form crossover locations withpickup lines, where the crossover locations are formed by folding thetop layer 1370 over bottom layer 1372, folding the flexible substrateupon itself about flex bend radius 1374. From a side view, the top flex1364 is layered over top soldermask 1362, which is layered upon topcopper or pickup lines 1360. Bottom layer solder mask 1370 is foldedunder top copper 1360, and bottom copper 1372 is formed under soldermask 1370 and over bottom flex 1375.

Referring to FIG. 13 b, an example of a module structure 1301 is shownfor mounting the flex layer structure 1300 of FIG. 13 a. Those skilledin the art will understand that the structure of a particular module mayvary according to the embodiment, and that this example, though it showsa substantially complete example of a module that can be used to base apractical implementation, is but one example and is not intended andshould not be considered as limiting the embodiment in any way. Theexample structure 1301 includes rigid substrate 1330 that receives theflex top layer 1370 on its top layer with flex locating pins or plasticframe 1337 configured to ensure alignment of the drive plates with thepickup plates. Because the sensing electrode pairs are formed bycrossovers of the drive and pickup lines on the two layers, the x-yalignment tolerance requirements may be on the order of several pixels,rather than the sub-pixel alignment tolerances that would be required ifthere were features to be matched between the two layers. The fourmounting holes (1337) on each layer are sufficient to ensure angular andx-y alignment. Also illustrated is driver chip 1310 and imaging area1350.

Referring to FIG. 14, an illustration is provided of an example system1400 incorporating a sensor system 1402 generally configured accordingto the embodiment. A sensor device may be incorporated into a system, ormay be configured as a stand-alone product. As a stand-alone product,the sensor components may be encased in a housing (not shown), andelectrical connections exposed for connection to a device or system thatwould utilize such a device. Those skilled in the art will immediatelysee how a sensor configured according to the embodiment as describedherein can be incorporated into a housing such as those that widely usedin different industry sectors. Thus, for example, in a system, themechanical connections, designs and structures may necessarily varyaccording to a particular application. For example, if incorporated intoa laptop for use as a fingerprint sensor, a surface mounting modulewould need to be employed to expose the sensor grid lines to a user. Ifincorporated into a mobile phone, personal data assistant (PDA) or thelike, another type of mounting module would be needed to conform to theparticular device design while providing the operational capability ofthe sensor. Again, FIG. 14 illustrates a diagrammatic representation ofa system 1400 that incorporates a sensor 1402 configured according tothe embodiment with the folded flexible or rigid substrate 1404 having atop layer 1406 and a bottom layer 1408, and each having either pickuplines or plates and drive lines or plates respectively depending on theapplication, though not shown here. The two-dimensional sensing area1411 is shown with an object 1410 on top, which may be a finger in thecase of a fingerprint sensor, or another object in another application.The top layer's pickup plates or lines (not shown) communicate with topplate processing circuitry 1410 via communication link 1412 to sendresultant signals received. Drive lines or plates are located but notshown here on bottom layer 1408, and receive drive signals from bottomplate processing circuitry 1414 via communication line 1416. The topplate processing circuitry 1410 includes front end buffers andamplifiers 1416 configured to receive, amplify and/or buffer or store aresultant signal received from the pickup plates or lines. A switcharray 1418 such as that illustrated in FIG. 9 is configured to receivethe signal from the front end 1416 and send the switched signal toanalog to digital (A/D) converter 1420 for conversion to a digitalsignal. Digital signal processor (DSP) 1422 is configured to receive thedigital signal from A/D converter 1420 and process the signal fortransmission.

Bottom plate processing circuitry 1414 is configured to produce a drivesignal for use by drive plates or lines located on the bottom layer 1408of the sensor substrate 1404, and includes drivers and scanning logic1424 for producing the signal, and programmable frequency generate 1426for programmable setting the frequency in which the drive signal is set.The bottom plate processing circuitry 1414 includes communication link1428, likewise, top plate circuitry has communication link 1420 forcommunicating with system buss 1432 for sending and receivingcommunications among the system, such as to processors, memory modules,and other components. System buss 1432 communicates with persistentmemory 1434 via communication link 1436 for storing algorithms 1428,application software 1440, templates 1442, and other code for persistentand frequent use by processor 1444. Processor 1444 includes processorlogic having logic and other circuitry for processing signals receivedfrom the system buss and originating from the sensor 1402, and alsoincludes arithmetic logic unit 1450 configured with logical circuits forperforming basic and complex arithmetic operations in conjunction withthe processor. Processor memory 1452 is configured for local storage forthe processor 1444, for example for storing results of calculations andretrieval for further calculations.

In operation, drive signals are controlled by processor 1444, andparameters for the drive signals originating from bottom plateprocessing circuitry 1414 are set in the bottom plate processingcircuitry 1414 by the processor 1444. Drive signals are generated bylogic 1424 within the parameters set in generator 1426 and sent tobottom plate 1408 via communication link 1416. These signals generateelectromagnetic fields that extend to pickup lines on top layer 1406about the sensing area 1411. These signals are cycled through differentpixel electrode pairs on the sensor grid (not shown here, but describedabove.), and some of these electromagnetic fields are absorbed by theobject 1410 (such as a fingerprint for example). The resultant signal ispicked up by the pickup plates or lines located on top layer 1406 aboutthe sensing area (not shown here, but described above.). The resultantsignal is then transmitted to top plate processing circuitry 1410 viacommunication line 1412, and the signal is processed and transmitted tostorage or processor 1444 for further processing. Once the drivers andscanning logic have cycled through the pixels on the grid sensor, datarelated to features and characteristics of the object can be defined andutilized by the system. For example, in a fingerprint sensor system, theimage may be a fingerprint image that can be compared to a storedfingerprint image, and, if there is a match, it can be used to validatea user.

FIG. 15 Illustrates how a device configured according to the embodimentmay be applied to a fingerprint sensing application. A user places afinger with fingerprint (1510) over the sensor grid, which is formed bythe crossover locations of the drive plates (1506 a-1506 n) and thepickup plates (1502 a-1502 m). Image pixel 1561 a senses the fingerprintarea above the electrode pair of drive plate 1506 a and pickup plate1502 a, pixel 1561 a senses the crossover of drive 1506 n and pickup1502 a, and pixel 1562 n senses the area above the crossover of drive1506 n and pickup 1502 m

FIG. 16 illustrates the steps required to collect the fingerprint imageas shown in FIG. 15, using the embodiment shown in FIGS. 11 and 14.Image capture begins at step 1601. As part of the initialization a rowcounter is initialized to 1 at step 1602. Step 1603 is the beginning ofa row scan sequence. At the beginning of each row, a column counter isset to 1 at step 1603. In step 1604, the top plate scanning logic 1145activates the appropriate analog switch (one of 1103 a through 1103 n)for the selected row. In Step 1605 the sense of an individual pixelbegins when the bottom plate scanning logic 1140 activates theappropriate drive plate (one of 1106 a through 1106 n) with the carriersignal 1116. At step 1606 the signal from differential amplifier 1180 issampled repeatedly by A/D converter 1125 after processing throughprogrammable gain amplifier 1190. Digital mixer 1118 mixes the samplesdown to the baseband frequency set by digital oscillator 1110. Thebaseband signal is then filtered by digital decimating filter 1120 toproduce a signal level value for the current pixel. The functionsperformed for this step in the embodiment of FIG. 11 could alternativelybe performed by the corresponding analog receiver shown in FIG. 10, orother functionally similar arrangements. In step 1607 the signal levelvalue derived in step 1606 is stored in the appropriate position inmemory buffer 1132 that corresponds to the currently selected row andcolumn. In step 1608 the column number is incremented, and in step 1609the column number is tested to determine whether the current rowcollection has been completed. If the row has not been completed, wereturn to step 1605 to collect the next pixel in the row. If the row iscomplete, we proceed to step 1610 and increment the row number. In step1611, we test the row number to determine if all the rows have beenscanned. If not, flow returns to 1603 to start the next row back at thefirst column. Once all the rows have been scanned, image capture iscomplete, and we proceed to step 1612, at which point the image is readyfor further processing or transfer to long term storage.

Those skilled in the art will recognize that row and column scanningorder may not correspond directly to physical position in the array, assome implementations may more optimally be sampled in interleavedfashions.

In FIG. 17, an example of the example as shown in FIG. 14 in a userauthentication application. In step 1701 a system level application 1440on processor 1444 requires user authentication. At step 1702 the user isprompted to provide a finger for verification. The system waits forfinger presence to be detected in step 1703. This can be performed bycollecting a reduced size image as described in FIG. 16 and testing forfinger image, or via other dedicated hardware. Once finger presence isdetected, a complete image is collected in step 1704, using the methoddescribed in FIG. 16 or other substantially similar method. This imageis then stored and in step 1705 converted into a template 1712 as shownin FIG. 17B, typically consisting of a map of minutia point locationsand types (such as bifurcations 1710, and terminations 1711), orpossibly of ridge frequency and orientation, or some combination ofboth. In step 1707 the template is then compared against one or moreenrollment templates that were retrieved from persistent templatestorage 1142 in step 1706. If a match is found, the user isauthenticated in step 1708 and granted access to the application. If nomatch is found, the user is rejected in step 1709, and access is denied.

In an authentication system such as described by FIGS. 16 and 17A-B,there can be a tradeoff between security and operational speed. A devicesuch as a smartphone may have differing security and convenience (speed)requirements for differing operating modes, as well. These tradeoffs maybe governed by the value of security for different types of information.As an example, users may place a low value on security for simplypowering up their smartphone or other device. But, they may place a muchhigher value on performing a financial transaction or other sensitivetransfer. They may want to lock out the ability to access personalcontact information or customer lists, or may also want to lock out theability for others to make local calls, long distance calls, accesspersonal photos, access social networking websites, sent and receivetext messages or emails, and they may want to have different securityprotocols for the access to different information. Users havingconventional systems without the benefit of biometrics will typicallylock their telephone handset with a four-digit PIN, which is a fairlylow level of security. Securing a financial transaction over the samedevice, a new development that is desired in the industry, would cause auser to desire a much higher level of security. Conversely, the amountof time a user would find acceptable to unlock the phone for a simplecall would be much shorter than the time they would wait to secure ahigh value transaction, where a user may be more tolerant of a highertime demand for authenticating the user for a financial transaction.

Embodiments described herein facilitate supporting both of theserequirements by providing variable captured image resolution andmatching algorithm security level. In one example, when operating inhigh security mode (such as when enrolling a user or validating ahigh-value transaction) the image capture procedure described in FIG. 16and the match procedure described in FIG. 17A-B may operate in fullresolution mode. When operating in ‘convenience’ mode (such as unlockingthe phone, looking at photos, surfing the internet or switching users),the fingerprint image may be acquired in a half-resolution mode byskipping every other column and every other row—for example where steps1608 and 1610 would increment the Column and Row counters, respectively,by two instead of one. This may result in an image with half theresolution in each axis compared to the high security mode, andone-fourth the size. This could cut by a factor of four both the timerequired to acquire the image (FIG. 16) and the time required to extractthe template from the image (step 1705). Due to the reduced resolutionof the image, and the relaxed security requirements for this conveniencemode, the matching threshold applied in step 1707 may be accordinglyreduced.

Referring to FIGS. 18A-D, another embodiment of a sensor module orassembly is illustrated as a sensor 1800, first shown in an expandedview in FIG. 18A, made up of a folded flex sensor 1802, a module foldingbase 1804 and mounting board 1806. In this embodiment, a switch having aplunger 1812 and base 1813 is incorporated into a sensor assembly thatallows the integration of the sensor operations, such as fingerprintsensor operations, together with other operations of a device. Stillfurther, this assembly allows for the configuration of a personalizationswitch for use on a device, such as a mobile telephone or smart phonefor example, that has extended functions including biometric operations.If used together with a power or selector switch, such as for example amodular replacement for the main selection switch on an iPhone™manufactured by Apple Computer Corporation or a navigation selectionswitch used on a BlackBerry™ smartphone manufactured by Research inMotion (RIM™) next to the display screen of these devices, a fingerprintsensor can be used for authentication while using these personaldevices. The authentication can be used to access the device entirely,access different levels of information such as different informationthat a user wishes to protect, or could be used for authentication ofthe user for financial transactions that require a higher level ofsecurity. These settings maybe preset by the manufacturer, may be resetby the user, may be set by a financial institution associated with theuser or the device, or may be configurable by anyone with an interest inprotecting the information.

Still referring to FIG. 18A, the folded flex sensor 1802 may be foldedat 1805 and 1807 respectively to fit about the module folding base 1804at mounting locations loop brace 1805-A and folding edge 1807-Arespectively, along with placement holes 1808 to aid in placing the flexabout the module and holding it in place. If the embodiments of the flexsensor circuit formed or otherwise configure on a substrate according tothe examples of FIG. 12A or 12B, different mounting operations may berequired to accommodate these or other designs that requires a differentfolding or forming of the substrate. The sensor 1802 may includeprocessor 1810 as described in similar embodiments above. Mounting board1806 includes a switch 1813 mounted about switch opening 1811 toaccommodate plunger 1812, and may also have a processor opening 1814configured to accommodate processor 1810.

Referring to FIG. 18B, another expanded view of the sensor of FIG. 18Ais shown from another angle, where one side of the flex sensor 1802shows more clearly the openings 1808 and processor 1810, where theopenings 1808 are configured to receive placement or mounting pegs 1816for holding the sensor 1802 substrate in place and then received bymounting openings 1818. The placement or mounting pegs 1820 are receivedby mounting openings 1822. Switch base opening 1824 is configured toreceive switch base 1813. In another embodiment, the opening for theplunger 1812 and the base 1813 may be a single sized opening that willaccept the entire switch, or the switch may have base with the samediameter as the plunger so that a single cylindrical or rectangular orother shaped opening may be sufficient to accommodate the switch.

FIG. 18C shows a side cut away view of the assembled sensor assemblywith the sensor substrate 1802 mounted on module folding base 1804 andmounted on base 1806, and with the openings 1811 and 1824 accommodatingthe switch plunger 1812 and switch base 1813 respectively. FIG. 18Dshows a close-up view of the side view of FIG. 18C.

FIGS. 19A-J show an alternative sensor/switch assembly where a domeswitch is used for the underlying switch that is integrated in theassembly. Referring to FIG. 19A, the assembly 1900 includes a domeswitch 1912 integrated with module folding base 1904 mounted on mountingboard 1906. In this embodiment, a switch having a domed shaped plunger1912 and base 1913 (FIG. 19C) is incorporated into a sensor assemblythat allows the integration of the sensor operations, such asfingerprint sensor operations, together with other operations of adevice.

Referring to FIGS. 19A, B and C, the folded flex sensor 1902 may befolded at 1905 and 1907 respectively to fit about the module foldingbase 1904 at mounting locations loop brace 1905-A and folding edge1907-A respectively, along with placement holes 1908 (FIG. 19D) to aidin placing the flex about the module and holding it in place. If theembodiments of the flex sensor circuit formed or otherwise configure ona substrate according to the examples of FIG. 12A or 12B, differentmounting operations may be required to accommodate these or otherdesigns that requires a different folding or forming of the substrate.The sensor 1902 may include processor 1910 as described in similarembodiments above. Mounting board 1906 includes a switch 1913 mountedbelow plunger 1912, and may also have a processor opening 1914configured to accommodate processor 1910 (FIG. 19D).

Referring to FIGS. 19G, H and I, side views of the sensor is shown,showing the flex sensor 1902 and the openings 1908 and processor 1910,where the openings 1908 are configured to receive placement or mountingpegs 1916 for holding the sensor 1902 substrate in place and thenreceived by mounting openings 1918. The placement or mounting pegs 1920are received by mounting openings 1922. Switch base opening 1924 isconfigured to receive switch base 1913. In another embodiment, theopening for the plunger 1912 and the base 1913 may be a single sizedopening that will accept the entire switch, or the switch may have basewith the same diameter as the plunger so that a single cylindrical orrectangular or other shaped opening may be sufficient to accommodate theswitch.

FIGS. 19E,F, and J show a normal, cutaway, and expanded cut away viewsof the sensor assembly mounted in a device such as a smartphone, withthe sensor substrate 1902 mounted on module folding base 1904 andmounted on base 1906, and with the openings 1911 and 1924 accommodatingthe switch dome plunger 1912 and switch base 1913 respectively. Thesensor area 1901 is accessed by a bezel opening 1909 which isincorporated into the finished case 1925 of the device. When the userplaces a finger on sensor surface 1901 they will simultaneously depressswitch plunger 1912.

FIG. 20 illustrates a perspective view of one embodiment of an embeddedswitch 2000 that can provide a means to electronically connect a topconductive layer 2002 through insulating layer 2004 to conductive layer2006 upon the touch of a user on the surface of the sensor, not shownhere, but it may be a layer above conductor 2002. The three layers maybe embedded within a fingerprint sensor as described above, allowing fora switch located within the double-layered fingerprint sensor, so that auser can activate a function upon touch, such as power, select,initiate, enter, or other switch functions in a device. The three layersmay be placed on a surface 2006 of module 2008, where the module islocated on the surface 2010 of a substrate 2012.

FIGS. 21A and 21B FIG. 21A shows an embodiment where a switch is formedon the same substrate as the sensor. The figures show the folded flexstack-up consisting of flex substrates 2102 and 2103, typically but notlimited to Kapton©, metalized layers 2104 and 2105 are typically etchedor formed copper traces and insulating layers 2106 and 2107 aretypically solder mask. Insulating layers 2106 and 2107 have a cutoutsection 2110 out exposing the conductive layers 2104 and 2105. When novertical pressure is applied over the gap 2110 conductive layers 2104and 2105 are not electrically in contact with each other and are in theoff position.

FIG. 21B shows the flex top layer 2103 and conductive layer 2112mechanically depressed by a contacting object such as a finger. Topconductive layer 2107 can be pushed physically into electrical contactwith conductive layer 2106 at pressure focal point 2112. This forms anembedded flex switch, which is shown in the on position.

FIGS. 22-26 illustrate alternative embodiments and further examples.These examples may be configured using different materials andstructures, and they may further be oriented or integrated in differentstructures such as power buttons in mobile devices, stationary devices,computers, laptops, access devices (doorknobs, entryways, or the like).Note that in these figures and the number of plates is greatly reducedto simplify the drawings, and the size of individual drive and pickupplates are increased for simplicity as well. In practice, both drive andpickup plates may be formed at fixed or variable pitch, and unlike thedrawings, the spacing between plates may be greater or less than theindividual plate size.

FIG. 22 depicts an embodiment where the drive and detection electronicsare implemented on separate silicon components. This configurationminimizes interconnect between layers by directly mounting the drive dieon the substrate layer for the drive lines, and directly mounting thepickup die on the substrate for the pickup plates. The rigid substratefor the drive plates also serves as a common base layer which providesinterconnect for synchronizing signals between the two subsystems, aswell as power and communications to the host device.

In this particular example, the common substrate (2201) is a two layerrigid circuit board, which also provides a mechanical base for thesensor. The drive circuitry is implemented in integrated circuit die(2204) which is mounted on rigid drive substrate (2201). The die isconnected to the circuit on the rigid substrate by a number of bondingpads (2206) using standard flip-chip mounting processes. A large numberof drive lines (typically more than 100) are connected to the driveplates (2209), which are formed on the top side of the rigid substrate.

A dielectric layer (2208) separates drive plates (2209) from pickupplates (2210). In this instance dielectric layer (2208) is provided by asolder mask layer applied to the drive plates (2209) and rigid substrate(2201).

Pickup substrate assembly (2202) with pre-attached pickup circuit die(2205) is mounted on top of drive substrate (2201). The die is connectedto the circuit on the flexible substrate by a number of bonding pads(2216) using standard flip-chip mounting processes. Because substrate(2202) is flexible, attach pads (2211) can mate with their correspondingpads (2212) on base substrate (2201). A cutout (2203) is provided inbase substrate (2201) to accommodate pickup chip (2205) so the assemblylies flat. Attach pads (2211) provide interconnect to the mating pads(2212) on the substrate layer (2201).

Interconnect traces (2214) formed on the top layer of base substrate(2201) provide synchronizing signals between the integrated circuits(2204) and (2205).

Interconnect traces (2215) in the base substrate (2201) route signals tointerconnect pads (2213) for power, ground, and communicationsinterconnect to the host system.

FIGS. 23 a-f illustrates an example of an assembly stackup of thetwo-chip. FIG. 23 a shows the rigid base (2201) with the drive plates(2209), host interconnect traces (2215) and contact pads (2213), pickupcommunications traces (2214) and contact pads (2212). Cutout (2203) ismad in base (2201) to accommodate the pickup IC which will be attachedin a subsequent step.

Rigid base (2201) could be fabricated from standard circuit boardmaterials, such as FR4, in which case plates (2209), interconnect (2213and 2214) and pads (2213 and 2212) would typically be formed from copperby use of circuit board etching techniques. Rigid base (2201) could alsobe formed from glass, in which case plates (2209), interconnect traces(2213 and 2214), and pads (2212 and 2213) would typically be formed froma transparent conductive material such as Indium-Tin Oxide (ITO).

FIG. 23 b shows drive electronics die (2204) attached to the traces onthe assembly from FIG. 23 a. The die is shown attached to the traces viastandard flip-chip mounting processes.

FIG. 23 c shows the exemplary assembly after the addition of dielectriclayer 2208. This dielectric layer may be formed by a standard soldermaskprocess, such as LPI, or by applying a piece of dielectric such asKapton film.

FIG. 23 d shows a cutaway view of the exemplary flexible substrate(2202) with pickup plates (2210) and pickup communications pads (2211)formed on it. Flexible substrate (2202) may be formed from a Kaptonfilm, in which case the plates (2210), traces, and pads (2211) wouldlikely be formed of copper by standard etching techniques. Flexiblesubstrate (2202) could also be made of a transparent material, such aspolyester, with plates, traces, and pads formed from by depositing afilm of a transparent conductive material such as ITO.

FIG. 23 e shows the cutaway view of the exemplary flexible substratewith the addition of pickup electronics die (2205). Electricalconnections between the die and elements on the flex are made by bondinginterconnect bumps (2216) on the die to contacts (2217) on the flexassembly, as shown in FIG. 22 e. Interconnect bumps (2216) are typicallymade of gold, while contacts (2217) are features formed of the samematerial as the plates and traces.

FIG. 23 f shows a cutaway view of the exemplary completed assembly, asthe flex assembly is mounted onto the rigid assembly. Electricalconnection between the two sub-assemblies is made by mating flexassembly pads (2211) to rigid assembly pads (2212).

FIG. 24 shows an example of steps required to assemble the exemplaryembodiment shown in FIGS. 22 and 23. In Step 2401 traces 2214 and 2215,host contact pads 2213, layer interconnect pads 2212, and drive plates2209 are all formed by an etching process on substrate 2201. A number ofinstances of the substrate assemblies may be formed at the same time byrepeating the pattern across a large panel of base material. In Step2402 cutout 2203 is formed in substrate 2203 by a standard circuit boardrouting process. This may take place at the same time that the multipleinstances of substrate 2201 are separated by cutting out the substrateoutline from the common panel. In Step 2403 dielectric layer 2208 iscreated by applying a layer of material such as LPI solder mask tosubstrate 2201 and drive plates 2209. In Step 2404 pickup plates 2210,interconnect pads 2211, and bonding pads 2217 are formed on substrate2202 by an etching process. In Step 2405, drive electronics die 2204 ismounted onto the substrate assembly 2201 using a standard chip-on-boardflip-chip bonding process. In Step 2406, pickup electronics die 2205 ismounted onto substrate assembly 2202 using standard flip-clipchip-on-flex bonding process. In Step 2407, flex substrate assembly 2202is mounted onto base substrate assembly 2201. In Step 2408 pads 2211 and2212 are electrically connected using an anisotropic conducting film(ACF) attach process.

FIG. 25 shows an embodiment where the drive and detection electronicsare implemented on separate structures, such as separate siliconcomponents for example. This configuration minimizes interconnectbetween layers by directly mounting the drive die on the substrate layerfor the drive lines, and directly mounting the pickup die on thesubstrate for the pickup plates. The drive and pickup layers may be bothconnected to a common base layer which provides interconnect forsynchronizing signals between the two subsystems, as well as power andcommunications to the host device. In this particular example, thecommon substrate (2500) may be a two layer rigid circuit board, whichmay also provide a mechanical base for the sensor. The drive circuitrymay be implemented in integrated circuit die (2504) that is mounted onflexible drive substrate (2501). The die may be connected to the circuiton the flexible substrate by a number of bonding pads (2506) usingstandard flip-chip mounting processes or other mounting processes knownin the art. A large number of drive lines (possibly 100 or more) may beconnected to the drive plates (2509), which may or may not be formed onthe same flexible substrate. Attach pads (2511) can provide interconnectto the mating pads (2512) on the substrate layer (2500). Substrate(2500) may incorporate a cutout (2513). In one example, the cutout maybe configured so that when the drive substrate (2501) is attached driveelectronics chip (2504) will not contact substrate (2501), and theassembly lies flat or planar. In another embodiment, a surface may notbe entirely planar or even molded over an object such as a power button,the different layers my have a cutout to accommodate differentstructures such as the drive electronics. Pickup substrate assembly(2502) with pre-attached pickup circuit die (2505) may be mounted on topof both drive substrate (2501) and base substrate (2500). In thisembodiment, drive substrate (2501) provides the dielectric layer betweenthe drive and pickup plates, without the need for a separate dielectriclayer as in previously discussed embodiments. If substrate (2502) isflexible, attach pads (2507 a) may be able to mate with theircorresponding pads (2507 b) on base substrate (2500). A cutout (2503)may be provided in base substrate (2500) to accommodate pickup chip(2505) so the assembly lies flat. Interconnect traces (2514) formed onthe top layer of base substrate (2500) may be included to providesynchronizing signals between the integrated circuits (2504) and (2505).Vias (2507 c) or other openings in the base substrate (2500) may be usedto route signals to the bottom layer, where lower layer traces (2509)may connect the signals to interconnect pads (2508) for possibly power,ground, communications interconnect to the host system, and otherconnections.

FIG. 26 shows an exemplary embodiment where the drive and detectionelectronics are both provided by a single integrated circuit. In oneexample, substrate (2601) may be composed of a dielectric material whichseparates the drive (2602) and pickup (2603) plates. Substrate (2601)may be a flexible material, such as Kapton, or a thin rigid material,such as an aramid laminate layer in a FlipChip package, or it may beanother material. Integrated circuit die (2604) incorporates contactpads (2611) which are mounted onto bonding pads (2605) the bottom layerof the substrate. The bonding pads provide connections from die (2604)to interconnect traces (2606), drive plates (2602), and pickupinterconnect traces (2607), A number of vias (2609) electrically connectpickup interconnect (2607) on the bottom layer to pickup plates (2602),which may be located on the top layer. Interconnect traces (2606) mayconnect die (2604) to host connector pads (2608). A dielectric layer(2610) may be formed atop pickup plated (2603) to prevent direct contactof the finger with the pickup plates. The dielectric layer (2610) may beformed from a number of materials, including but not limited to an LPIsoldermask material, an ink, or a top kapton coversheet. In anotherembodiment, a surface may not be entirely planar or even molded over anobject such as a power button,

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad embodiment, andthat this embodiment is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. Hence, alternativearrangements and/or quantities of, connections of various sorts,arrangements and quantities of transistors to form circuits, and otherfeatures and functions can occur without departing from the spirit andscope of the embodiment. Similarly, components not explicitly mentionedin this specification can be included in various embodiments of thisembodiment without departing from the spirit and scope of theembodiment. Also, different process steps and integrated circuitmanufacture operations described as being performed to make certaincomponents in various embodiments of this embodiment can, as would beapparent to one skilled in the art, be readily performed in whole or inpart to make different components or in different configurations ofcomponents not explicitly mentioned in this specification withoutdeparting from the spirit and scope of the embodiment. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad embodiment, andthat this embodiment is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Again, the embodiment has application in many areas, particularly inbiometric sensors. Fingerprint sensors, for example, and other biometricsensors are gaining increasing acceptance for use in a wide variety ofapplications for security and convenience reasons. Devices, systems andmethods configured according to the embodiment will have improvedsecurity of the biometric verification process without increasing thecost of the system. Furthermore, the embodiment may extend to devices,systems and methods that would benefit from validation of components. Asdiscussed above, the embodiment includes the ability for the host andsensor to include any combination or subset of the above components,which may be arranged and configured in the manner most appropriate forthe system's intended application. Those skilled in the art willunderstand that different combinations and permutations of thecomponents described herein are possible within the spirit and scope ofthe embodiment, which is defined by the appended Claims, theirequivalents, and also Claims presented in related applications in thefuture and their equivalents.

The embodiment may also involve a number of functions to be performed bya computer processor, such as a microprocessor. The microprocessor maybe a specialized or dedicated microprocessor that is configured toperform particular tasks according to the embodiment, by executingmachine-readable software code that defines the particular tasksembodied by the embodiment. The microprocessor may also be configured tooperate and communicate with other devices such as direct memory accessmodules, memory storage devices, Internet related hardware, and otherdevices that relate to the transmission of data in accordance with theembodiment. The software code may be configured using software formatssuch as Java, C++, XML (Extensible Mark-up Language) and other languagesthat may be used to define functions that relate to operations ofdevices required to carry out the functional operations related to theembodiment. The code may be written in different forms and styles, manyof which are known to those skilled in the art. Different code formats,code configurations, styles and forms of software programs and othermeans of configuring code to define the operations of a microprocessorin accordance with the embodiment will not depart from the spirit andscope of the embodiment.

Within the different types of devices, such as laptop or desktopcomputers, hand held devices with processors or processing logic, andalso possibly computer servers or other devices that utilize theembodiment, there exist different types of memory devices for storingand retrieving information while performing functions according to theembodiment. Cache memory devices are often included in such computersfor use by the central processing unit as a convenient storage locationfor information that is frequently stored and retrieved. Similarly, apersistent memory is also frequently used with such computers formaintaining information that is frequently retrieved by the centralprocessing unit, but that is not often altered within the persistentmemory, unlike the cache memory. Main memory is also usually includedfor storing and retrieving larger amounts of information such as dataand software applications configured to perform functions according tothe embodiment when executed by the central processing unit. Thesememory devices may be configured as random access memory (RAM), staticrandom access memory (SRAM), dynamic random access memory (DRAM), flashmemory, and other memory storage devices that may be accessed by acentral processing unit to store and retrieve information. During datastorage and retrieval operations, these memory devices are transformedto have different states, such as different electrical charges,different magnetic polarity, and the like. Thus, systems and methodsconfigured according to the embodiment as described herein enable thephysical transformation of these memory devices. Accordingly, theembodiment as described herein is directed to novel and useful systemsand methods that, in one or more embodiments, are able to transform thememory device into a different state. The embodiment is not limited toany particular type of memory device, or any commonly used protocol forstoring and retrieving information to and from these memory devices,respectively.

The term “machine-readable medium” should be taken to include a singlemedium or multiple media (e.g., a centralized or distributed database,and/or associated caches and servers) that store the one or more sets ofinstructions. The term “machine-readable medium” shall also be taken toinclude any medium that is capable of storing, encoding or carrying aset of instructions for execution by the machine and that causes themachine to perform any one or more of the methodologies of the presentembodiment. The machine-readable medium includes any mechanism thatprovides (i.e., stores and/or transmits) information in a form readableby a machine (e.g., a computer, PDA, cellular telephone, etc.). Forexample, a machine-readable medium includes memory (such as describedabove); magnetic disk storage media; optical storage media; flash memorydevices; biological electrical, mechanical systems; electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.). The device or machine-readablemedium may include a micro-electromechanical system (MEMS),nanotechnology devices, organic, holographic, solid-state memory deviceand/or a rotating magnetic or optical disk. The device ormachine-readable medium may be distributed when partitions ofinstructions have been separated into different machines, such as acrossan interconnection of computers or as different virtual machines.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad embodiment, andthat this embodiment not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Reference in the specification to “an embodiment,” “one embodiment,”“some embodiments,” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments. The various appearances “an embodiment,”“one embodiment,” or “some embodiments” are not necessarily allreferring to the same embodiments. If the specification states acomponent, feature, structure, or characteristic “may”, “might”, or“could” be included, that particular component, feature, structure, orcharacteristic is not required to be included. If the specification orClaim refers to “a” or “an” element, that does not mean there is onlyone of the element. If the specification or Claims refer to “anadditional” element, that does not preclude there being more than one ofthe additional element.

The methods, systems and devices include improved security operationsand configurations with a novel approach to biometric systems. Suchsystems would greatly benefit from increased security features,particularly in financial transactions. Although this embodiment isdescribed and illustrated in the context of devices, systems and relatedmethods of validating biometric devices such as fingerprint sensors, thescope of the embodiment extends to other applications where suchfunctions are useful. Furthermore, while the foregoing description hasbeen with reference to particular embodiments of the embodiment, it willbe appreciated that these are only illustrative of the embodiment andthat changes may be made to those embodiments without departing from theprinciples of the embodiment, the scope of which is defined by theappended Claims and their equivalents.

The invention claimed is:
 1. An impedance sensor, comprising: aplurality of substantially parallel drive lines configured to transmit asignal to a proximally located object; and a plurality of substantiallyparallel pickup lines oriented substantially perpendicular to the drivelines and separated from the pickup lines by a dielectric to formintrinsic electrode pairs that are impedance sensitive at each drive andpickup crossover location.
 2. The impedance sensor according to claim 1,where the plurality of substantially parallel pickup lines have variablepitch.
 3. The impedance sensor according to claim 1, where the pluralityof substantially parallel pickup lines have variable line width.
 4. Theimpedance sensor according to claim 1, where the plurality ofsubstantially parallel pickup lines operate with a duty cycle differentfrom fifty percent.
 5. The impedance sensor according to claim 1, wherethe plurality of substantially parallel pickup lines operate with a dutycycle that is about fifty percent.
 6. The impedance sensor according toclaim 1, where the plurality of substantially parallel drive lines havevariable pitch.
 7. The impedance sensor according to claim 1, where theplurality of substantially parallel drive lines have variable linewidth.
 8. The impedance sensor according to claim 1, where the pluralityof substantially perpendicular drive lines operate with a duty cycledifferent from fifty percent.
 9. The impedance sensor according to claim1, where the plurality of substantially parallel pickup lines operatewith a duty cycle of about fifty percent.
 10. The impedance sensoraccording to claim 1, wherein the dielectric is a flexible substratehaving both the drive lines located proximate one side of the dielectricand the pickup lines located proximate an opposite side of thedielectric.
 11. The impedance sensor according to claim 1, wherein thedielectric is a rigid substrate having both the drive lines locatedproximate one side of the dielectric and the pickup lines locatedproximate an opposite side of the dielectric.
 12. The impedance sensoraccording to claim 1, further comprising a first substrate having thedrive lines located proximate one surface of the first substrate and asecond substrate having the pickup lines located proximate one surfaceof the second substrate.
 13. The impedance sensor according to claim 12,wherein the first and second substrates have individual electricalconnections.
 14. The impedance sensor according to claim 12, wherein thefirst and second substrates have individual electrical connectionsconnected to separate control processors.
 15. The impedance sensoraccording to claim 12, wherein the first and second substrates haveindividual electrical connections connected to a common controlprocessor with additional electrical connections between the first andsecond substrates.
 16. The impedance sensor according to claim 12,wherein the first and second substrates are flexible substrates withindividual input and/or output connections.
 17. The impedance sensoraccording to claim 12, wherein the first and second substrates includeone flexible substrate and one rigid substrate having individual inputand/or output connections.
 18. The impedance sensor according to claim1, wherein the drive and pickup lines include a substantiallytransparent conductor material and the dielectric is made from asubstantially transparent dielectric material.
 19. The impedance sensoraccording to claim 1, wherein the drive and pickup lines include asubstantially transparent conductor material and the dielectric is madefrom a substantially transparent dielectric material.
 20. The impedancesensor according to claim 19, wherein the drive and pickup lines haveindividual electrical connections.
 21. A fingerprint sensing system,comprising: a layered planar fingerprint sensor array configured toreceive a static fingerprint image; and a switch embedded within thelayered fingerprint sensor array in a manner that allows a user tocontact the switch simultaneously while contacting the sensor array. 22.The system according to claim 21, wherein the switch is furtherconfigured to allow a user to actuate the embedded switch simultaneouslywhile contacting the sensor.
 23. The system according to claim 21,wherein the switch is further configured to allow a user to depress asecond switch simultaneously while contacting the sensor.
 24. The systemaccording to claim 21, wherein the switch and fingerprint sensor arrayare configured to allow a user to contact the switch to provide power tothe sensor and to initiate a user validation sequence that authenticatesthe user fingerprint against one or more previously stored in memorybefore granting user access to the device.
 25. The system according toclaim 21, wherein the switch and fingerprint sensor array are configuredto allow a user to contact the embedded switch to provide power to thesensor and to simultaneously initiate a user validation sequence thatauthenticates the user fingerprint against one or more previously storedin memory before granting user access to the device.
 26. The systemaccording to claim 21, wherein the layered planar fingerprint sensorincludes a first layered substrate having drive lines with electricalconnections layered on a second layered substrate having pickup linesand electrical connections.
 27. The system according to claim 21,wherein the layered planar fingerprint sensor includes a first layeredsubstrate having drive lines with electrical connections for connectingto a digital circuit that is layered on a second layered substratehaving pickup lines and electrical connections to be connected to ananalog circuit.
 28. The system according to claim 21, wherein thelayered planar fingerprint sensor includes a first layered substratehaving drive lines with electrical connections to a multifunction hostprocessor circuit and a second layered substrate having pickup lines andelectrical connections to be connected to an analog processing circuitthat sends signal back to the host processor.
 29. The system accordingto claim 22, wherein the layered planar fingerprint sensor includes afirst layered substrate having drive lines with electrical connectionsto a multi-function host processor circuit and a second layeredsubstrate having pickup lines and electrical connections to be connectedto an analog processing circuit that is also located inside themultifunction host processor.
 30. An impedance sensor, comprising: afirst substrate having a plurality of substantially parallel drive linesconfigured to transmit a signal to a proximally located object; and asecond substrate substantially parallel with the first substrate andhaving plurality of substantially parallel pickup lines orientedsubstantially perpendicular to the drive lines to form an impedancesensitivity pair at each drive and pickup crossover location.
 31. Thesystem according to claim 30, wherein the drive lines have electricalconnections for communicating with a digital circuit and wherein thepickup lines for communicating with electrical connections to beconnected to an analog circuit.
 32. The impedance sensor according toclaim 30, wherein the first and second substrates have individualelectrical connections connected to separate control processors.
 33. Theimpedance sensor according to claim 30, wherein the first and secondsubstrates are flexible substrates with individual input and/or outputconnections.
 34. The impedance sensor according to claim 30, wherein thefirst and second substrates include one flexible substrate and one rigidsubstrate having individual input and/or output connections.
 35. Asensor, comprising: a plurality of drive lines configured to transmit asignal to a proximally located object; and a plurality of pickup linesthat cross over and are electrically separated from the drive lines toform impedance sensitive electrode pairs at each drive and pickupcrossover location.
 36. An impedance sensor, comprising: a rigidsubstrate; a plurality of drive lines mounted on the rigid substrate; aflexible substrate located above the rigid substrate; a plurality ofpickup lines mounted on the flexible substrate; and an insulating layerseparating the plurality of drive lines and the plurality of pickuplines.
 37. The impedance sensor of claim 36, wherein the plurality ofpickup lines are mounted on a lower side of the flexible substrate. 38.The impedance sensor of claim 37, further comprising: a drive circuitmounted on the rigid substrate and electrically connected to theplurality of drive lines, wherein the drive circuit is configured toapply a drive signal to one or more of the plurality of drive lines; apickup circuit mounted on the lower side of the flexible substrate andelectrically connected to the plurality of pickup lines, wherein thepickup circuit is configured to process signals from the plurality ofpickup lines.
 39. The impedance sensor of claim 38, wherein the rigidsubstrate forms a cutout, and wherein the pickup circuit is partiallyenclosed by cutout.
 40. The impedance sensor of claim 39, wherein thecutout is formed as a via that extends through the base substrate. 41.The impedance sensor of claim 38, wherein the pickup circuit comprisesconductive pads on its upper surface, and wherein the conductive padsare arranged to substantially correspond with the plurality of thepickup lines.
 42. An impedance sensor, comprising: a rigid substrate; afirst flexible substrate located above the rigid substrate; a pluralityof drive lines mounted on the first flexible substrate; a secondflexible substrate located above the rigid substrate; a plurality ofpickup lines mounted on the second flexible substrate, wherein thesecond flexible substrate electrically insulates the plurality of drivelines from the plurality of pickup lines.
 43. The impedance sensor ofclaim 42, further comprising: a drive circuit mounted on the firstflexible substrate and electrically connected to the plurality of drivelines, wherein the drive circuit is configured to apply a drive signalto one or more of the plurality of drive lines; a pickup circuit mountedon the second flexible substrate and electrically connected to theplurality of pickup lines, wherein the pickup circuit is configured toprocess signals from the plurality of pickup lines.
 44. The impedancesensor of claim 43, wherein the drive circuit is mounted on a lower sideof the first flexible substrate and the pickup circuit is mounted on alower side of the second flexible substrate.
 45. The impedance sensor ofclaim 44, wherein the rigid substrate forms a first cutout, and whereinthe drive circuit is partially enclosed by the first cutout, and whereinthe rigid substrate forms a second cutout, and wherein the pickupcircuit is partially enclosed by the second cutout.